There are two rats in this room… Let’s make rats interesting!

A trap, a power, an NPC and a Character Class for your rat-flavoured games using B/X stats.

New Trap | Rat Nest

You have fallen into a burrow full of rats, thousands of them.

Each round you suffer 3d4 points of damage, save vs paralyzation for half damage. In one round you can light a torch but that round you cannot save vs paralyzation. The light and fire keep the rats at bay for 1d4 rounds, after that, they get bold and rush at you.

New Power | Command Rats

Depending on the system you use and your preference, Command Rats can be a spell or an innate or acquired ability. The mechanics are less important than the effects.

Vancian Magic: Level-1 Spell. Duration: The Magic-User’s level in turns.

Otherwise: Innate, acquired, purchased, through an item, granted by King Rat, whatever. Duration: 1d10 turns or referee’s choice. User per day: Charisma’s modifier, minumum 1.

Effect: You can control a group of 1d6+9 rats to act in unison. The group has HP equal to the number of individuals, and will disperse when half of its members are lost or when the effect runs out. You can give them an order and they’ll carry it out to the best of their ability, as long as it’s not an order directly harmful to them.

Secondary Effect: When using this power, and for 1d4 days thereafter (cumulative), you’ll be constantly surrounded by friendly rats, they’ll climb on your shoulders, run around you, etcetera, but the intense light and fire will keep them away.

New NPC | King Rat

Leather Armor, HD 3, HP 12, Weapons 2 katara (push dagger) for a total of 1d8 damage (when attacking using only one, damage is 1d6).

King Rat is a man of about 45, handsome but slovenly, who lives in the catacombs, surrounded by rats who obey him and with whom he can talk, mainly about poetry, philosophy, politics and science; whether the rats understand or respond to him is open to debate. An anarchist, he doesn’t believe in authority but believes in fair exchange.

Command Rats: He can use this ability 5 times a day. How did he get it? If questioned and he decides to tell, he will say that it was given to him by God Rat, but will not give further details. King Rat doesn’t have any scarification.

Mark of the Rat: An adventurer can fulfill an assignment in exchange for the Mark of the Rat, which allows him to use Command Rats as described above. The Mark is a rat-shaped scarification on the left temple.

New Class | Rat Catcher

Only the man who cleans the public latrines has a worse job than you. But after all, you are not cut out for a glamorous life, nor are you cut out to rub elbows with the nobility or to know carnal love. But such trifles don’t matter to you, or at least you’ve managed to convince yourself of that. The alternative is very depressing.

A rat-catcher. [Source]
Requirement: DEX 9
Prime Requisite: CHA
HD: d6
Max Level: 14
Armor: Leather
Weapon: Any
Languages: Common, Thieves’ Cant


Poverty, or as you call it: freedom, is your motto. You are not used to wearing armor heavier than Leather; if for some reason you wear it, you can’t use your Knave, Track Vermin and Rat Senses abilities, and you lose 2 or 4 points of DEX while wearing it (Chainmail and Plate, respectively).

Gallows Humour

You get a +2 bonus to your rolls to resist psychological effects, magical or otherwise, related to fear, sadness or nihilism.


You know one Thief Skill of your choice (or randomly for more fun), except Find/Remove Trap and Pick Pocket. You can use it as a Thief of the same level.

Rat Senses I

You’re good at finding your way around sewers, catacombs, dark alleys and other artificial or semi-artificial structures. If you are the party’s cartographer, the referee is obliged to make at least one major correction or any number of minor corrections she wishes. When you come to a room or hallway that you have already visited, you always know that you have been there before and notice any relevant changes.

Rat Senses II

When you are in a dilemma between several possible paths, there is a 2-in-6 chance that you will instinctively know if there is any immediate danger (such as traps or an ambush).

Track Vermin

You can automatically detect and track vermin, including kobolds, goblins and the like (referee’s choice), and of course rat-folk. When you fight these creatures, your Thac0 receives a bonus of 1 (19 becomes 18, etc.)

9th Level

You can completely clear and control a major area of the city’s drainage system, subway tunnels or alleys, an area that will serve as your territory. You will be the leader of a gang of 2d6 thieves and 3d4 0-level beggars who will follow you and protect the territory, and will be happy to pay a small voluntary weekly tribute as long as you don’t show yourself to be a despot or start bathing more frequently than them, you fop!

Starting Gear (roll 1d30 three times)

1. Antivenom. 2. Dark clothes. 3. Stolen letter. 4. One-use lockpick. 5. Rope (10 m.) 6. Rusty knife (d4 dmg.) 7. Mud protecting boots. 8. Stinky wheel of cheese. 9. Book of satyrical and anarchist poetry against current authorities and the church. 10. Five rat traps. 11. Wooden plank (d6 dmg.) 12. A blood-stained nobility title. 13. Five flashing bomb flasks. 14. Flask of oil. 15. Five torches, tinder and flint. 16. Bronze key to a missing stash. 17. Valuable-looking book you can’t read full of demonic symbols. 18. Box containing five vials of mysterious sludge. 19. Old backpack. 20. Black hat. 21. Dog. 22. The sword of a nobleman (1d8 dmg), anyone who sees it will know it was stolen. 23. Eye patch. 24. Mantle. 25. Soft, stealth shoes. 26. Garish clothes. 27. Frying pan. 28. Crowbar. 29. Sling and ten stones (1d4 dmg.) 30. Cage of 1d4 live rats.

Level Progression

More rats? More rats!

Christmas theme entry | Consumerism in your OSR games

The christmas spirit is in the air, releasing its stinky pheromones that washes our brains into thoughtless consumerism. Let the spirit invade your game world with this brand-new option for your players’ characters to spend their hard-earned silver pieces on.

Elfpunk. The suspicious man in the black cloak with the weird eye is actually a barber surgeon who can medieval/cyber-improve you with “The red eye of sleep”, a magically imbued red orb the size of an eye that, when encrusted in your forehead, allows you to cast the spell Sleep once a day even if you are not a caster. 10,000 gold.

Pay for protection. The crazy old woman, “Mad Hattie”, needs 5,000 gold. If you refuse to give it to her, she will curse you. Her curses are level 5 necromantic spells.

A much needed cure. That mad old woman, “Crazy Hattie”, can remove any curse from you. It will cost you 6,000 gold only.

Combat options. Dr. Brain, actually a mi-go in disguise, but a civil one, can remove those extra bones from your hip and chest, allowing you to have an extra attack every two rounds (round 1 two attacks, one on your turn, another last; round 2 one attack on your turn; round 3 two attacks again…) It will cost you, 12,000 gold and one point of permanent Constitution.

A time for introspection. When you kill, you accumulate bad blood points equal to the monster’s or npc’s XP. When you reach 1,000 bad blood points, all your rolls are done at -1. When you reach 2,000 bad blodd points, they are done at -2. And so on. Remember that weird man in the black robes by the temple, with the scary laugh? He will relieve you of your sins… for a price. One bad blood point per 1 gold coin is erased from your name in the book of names that keep record of all your sins (and therefore these penalties).

Festive merriment. The PCs arrive in town in the middle of some festivity or another, and forced to break through with money and gossip. Each piece of useful information, rumor or clue will cost them 200 gold, modified by their charisma (a +2 grants a 20% discount; a -2 costs them 20% more).

Books. You see that lady in the long black overcoat? She sells dangerous things. Poison, thief tools, dark charms. Books. Her books, while owned, grant you a bonus to a specific action or area of knowledge. Maybe an extra +1 to saving throws versus poison or a free re-roll when a climbing roll is failed. Is she doesn’t have a book on the matter you want, she can get it, for an extra 100-500 gold, of course. 1,000 gold per book is quite reasonable, right? But there are some forbidden tomes that would cost much more than that.

Personal training. Pay a teacher and in one week, gain one skill point (LotFP skills) or 15% in a skill (B/X thief skill). Only 5,000 gold.

Liquid courage. 500 gold will get you a bottle of dwarven ale. In combat, you gain +1 to attack rolls but -1 to AC (but your AC can’t be lower than the unarmored value).

Fulfill your heart’s desire. Lovelie’s is open for business. Some work might be needed, but Lovelie’s night therapy will improve you. Whether this means you gain a permanent point in one stat, XP enough to reach your next level, the ability to never be surprised, or being irresistable to the same or the other sex, she can do it. But her services are not cheap.

If you need more option, check The Goatman’s Goblet. He has a good list!

Christmas merriment


Opposed rolls in old school games

If two characters want to compete to know who wins a bras de fer competition, or if they are engaged in a game of cards or chess, or any other situation where there cannot really, or should, be a draw, both roll 1d6 and add their most appropriate ability modifier (strength for a arm wrestling, wisdom for domino, charisma for a duel of looks, agility for throwing darts, constitution to endure without breathing, intelligence to solve an equation, etc.)

If there is a tie, another roll is made until there is a winner.

Sometimes it is a good idea to put some tension into these competitions. In those cases, the winner will be the first to achieve 3, 5, 10 or even more victories, for example in a long desert marathon or to determine who finds more decorated stegosaurus eggs at the Volcano Festival.

duel of looks

What’s a good trap? + Crown of Negativity

Into the Trap

I’ve been flipping through Grimtooth’s Ultimate Traps Collection, which is huge and full of ideas, just as perverse one than the last, but not as easy to use without some preparation work (some traps are one or two full pages long, and include diagrams; you can’t read that mid-session, you need to learn how the trap works before the game starts).

I also have been thiking about what Chris McDowall means when he says traps should be obvious:

Then he gives two examples:

This means there are no passive rolls to detect traps, but also that the player doesn’t need to actively search for traps (making the referee specific questions) to detect them.

Does it mean that characters in Into the Odd automatically detect traps? It seem so. So traps are fun not because they can harm the characters, are they fun, then, because characters can trump them? I am not sure Chris McDowall implies that, but it’s unlikey he means the opposite.

When I write a dungeon, I always want to add some traps but I always struggle to make interesting traps that are fun not matter if they are activated or bypassed. It’s not a easy job. What’s a good trap?

In this entry, he lists 34 traps and says these are the rules to make a good trap:

  • At least one part of it is immediately visible.
  • It allows interaction and investigation.
  • It has impactful consequences for the victim.

Let’s see a few:

  • Metal sword audibly humming, hooked up to electric charge.
  • Green Devil Face with gaping mouth. Anything going into the mouth is annihilated.
  • A fishing rod propped up and cast into a lake. The rod is covered in fast-acting glue and tension on the line triggers a springboard beneath the victim, casting them into the lake.

If you touch the sword, you suffer damage. To remove it, you should wear special gloves or find a way to cut the charge. But that’s a lot of trouble for a sword. That trap is there just to deal some damage to a character, it’s not a trap you would want to overcome, you simple don’t touch it.

If you enter the gaping mouth, you die. No save vs death roll, no nothing. You die. Sounds harsh but no sane person would enter a gaping mouth like that, right? Well, no sane person would be exploring dungeons, either. This trap is put there just to fuck the players, to teach them you must not interact with the features of the dungeon, or at elast, not with every feature, specially if it is a green devil face.

The fishing rod is another “fuck you” trap.

Unavoidable traps, then. Except, that is not really the case.

This article, and Into the Odd, assume, or at least expect, for the players to inspect the metal sword, the devil face and the fishing rod BEFORE they interact with them.

When a player inspects the sword (At least one part of it is immediately visible), she must explain what her character does, exactly (It allows interaction and investigation). If it makes sense, the referee then grants her the information about the trap. If the character makes something that triggers the trap (“I put a finger on the tip of the hilt”, “I enter the hole and go to sleep; it’s getting late”), she suffers the effects of the trap, electric discharge or sudden and instant death (It has impactful consequences for the victim). No rolls are made, other than damage.

In other words, a trap is triggered automatically if a character interacts with it incorrectly.

Sounds hardcore, but since rolls to detect traps aren’t required, it’s actually pretty easy to spot the trap. That’s not the important part. The important part is choosing between finding a way to disable the trap or just ignore it and move on.

So far, so good. It works well in a game like Into the Odd, which is pretty minimalistic and everything runs fast, and which most people seem to consider better for one-shots and short adventures, not for long-term campaigns (understandable since the game offers little concerning advancement mechanics and benefits).

Does it work for more traditional, Moldvayian (or Gygaxian) games?

Enter BX and Old-School Essentials

OSE, following BX, states that

Using the same examples from before, the sword and the rod are triggered by touching them, and the devil face is triggered by entering its gaping mouth. But traps don’t trigger automatically. When a character makes an action that would trigger the trap, the referee must roll 1d6, and if it comes up 1 or 2, the trap works; otherwise, it doesn’t work against that specific character. Other characters making a triggering action require their own 1d6 checks.

If we follow Moldvay’s steps closely, then there’s another problem:

Let’s obviate for the moment that only Thieves can detect and disable “treasure traps”, which is the name Moldvay and OSE give them, but which not necessarily are traps found in treasure items; Moldvay also simply refers to them as “small traps”, and the example given is a lock.

Anyway. Are these room or treasure traps?

The green devil face is big enough, and should clearly be considered a room trap (so anyone can detect it, 1-in-6 chance). The sword and the fishing rod are most probably small traps because the traps are placed on an item, but not “to prevent it being tampered with or stolen” (the evil orcs are not trying to protect neither the sword nor the rod), but then why?

Still, the three features are obvious, so when the party enters their respective rooms, the referee would state that there is a sword stuck in a stone, or lying on a slab; a wall covered by a big green devil face with the mouth opening the size of a priest-hole; and a lake, next to which there’s a fishing rod propped on and cast into it.

“What are you going to do?”

If a player says he touches either the sword or the rod, or enters the devil’s mouth, the referee rolls the trigger check, and, if needed, also rolls damage. In some cases, it’s stated that a Saving Throw is needed to avoid the effect.

But sometimes damage (or other effect) is automatic. That sounds worse than it actually is, remember that traps are not triggered automatically even if a charatcer interacts with it incorrectly.

Risk can be lowered even further, even if a trap is hidden, simply because there’s a mechanic to detect room traps:

And a mechanic to detect and disable treasure traps (only for Thieves):

There are no mechanics to disable room traps, but that’s just natural, since most traps that fall into that category are not meant to be disabled but bypassed, and it depends on the player’s ingenuity more than on a mechanical standard. A pit in a room can be bypassed by jumping, placing a wooden table as a bridge, by a flight spell, or using a rope to descend and then climb from the other end, each solution requiring its own unique roll, if at all.

Hidden Traps. Something else

Into the Odd disencourages the use of hidden traps. Since there is not a mechanical way to avoid a trap, hidden traps feel cheap and bullshit.

But classic D&D inspired games, with their triggering, Saving Throw mechanics, detecting and possibly dissabling or bypassing mechanics would not suffer from that, most of the time. Instadeath traps first have to be triggered, which is not automatic, and can also be detected and disabled/bypassed, then the player has a chance to avoid death making a saving throw. If he dies, it’s his damn fault.

Crown of Negativity | A (good? bad?) trap

So, this is me trying to make a good trap. But this is also me doing what I like: screw with the (campaign) world and the adventurers. Finally, this is what happens when I listen to Tool’s Lateralus (their only good album, which I must have listened to more than 5,000 times for the last 20 years) when I write.

A room in a dungeon

A boarded door (secret door roll) in a dark hallway leads to this room.

This room is different, maybe it’s dimly lit and there are purple or crimson courtains, while the rest of the rooms are crude and dilapidated; or, on the contrary, it’s ruined and full of dust, while the rest are tidy or sumptuous.

There is an altar, and a medium size wooden chest, chained, barb wired, and locked. A dry skeleton lies next to it. “Someone doesn’t really wanted this opened.”

Tell the players that a Thieve’s Remove Traps roll is needed to avoid damage from the barbed wire (1d4, perhaps). No other trap is present. If there is no Thief in the party, or if they come up with a different solution, let them try.

Inside there is a black crown, looks like obsidian or basalt, but it’s harder than steel, harder than any material you know. It seems to radiate darkness, or better, to devour the few photons around it.

“What do you do?” Ask them.

“I put the crown on”.

The person who puts on the crown, must pass a Saving Throw vs Spells, and in a failure, disappears completely, the crown falls to the floor, making no sound, as though it also devoured soundwaves.

If someone else puts the crown, it doesn’t trigger its effect, no saving throw is rolled.

Go back to the first one who failed the ST.

When you put on the crown, you feel your body disappear and now you’re falling into darkness. The crown is no longer on your head. There is someone else there, you can’t see it but you can feel it. It is a darkness in the dark.

Its voice speaks directly to your mind: “I can help you get out of here, my child. Just wear my crown on your head.” You can feel that it is handing you its crown, but some afterimages form in your mind: if you wear the crown, yes, you can come out of this well of darkness, but your body will be possessed by that other darkness, whose name, you know as well, is Grudge, who others call Saturn for it habit of eating its children.

There’s no salvation for you. If you leave this well of darkness, your body will cease to be yours and you will only exist as a remnant in Grudge/Saturn’s memory, ignorant to the damage done (but see the next section).

If you stay here, you will prevent that darkness from invading the world, but your only company will be the darkness and the darkness in it, to the lonesome end. Worst part? All this pain is not an illusion.

Hope this is what you wanted.

Hope this is what you had in mind.

’cause this is what you’re getting.

What I did here

There are obvious hints that the trap is there, that it is not a good idea to open the box. The room is concealed behind a secret door. The crown is hidden inside a protected box. The players don’t have a reason to put on the crown, but they still might (the fun in these games comes from experimenting and interacting with the environment, right?) The first character to do so still has a chance to avoid the consequences of the fatal mistake in the form of a Saving Throw.

It all comes down to one bad choice: wearing the crown.

Once a character fails that Saving Throw, he’s as good as dead.

If you want, you can ask for a Saving Throw vs Posion or Death one the player accepts the second, abstract crown. If he fails, he is devoured and his essence no loger exists, only his body, now possessed by the dark god. If he succeeds, though, he will live inside the god, unable to influence its behavior or controlling his own body. He will be the eternal spectator. And you better come uo with a very dark and very bleak and very grim spectacle, please. A world-changing event, maybe light ceases to exist in this planet, and only magical light is possible, but scarce.

If this trap was made with Into the Odd in mind, instead of rolls, everything is automatic once a character interacts correctly with each element. Traps don’t work (and cause disaster) because they follow a series of mechanics and the dice hate you*. Traps work (and cause disaster) because you make the wrong choices.

This trap can’t be disabled, the only way to bypass it is ignoring it entirely. Next time I should write one that can actually be disabled and bypassed by actively interacting with it.

*Magical thinking is bad for you.

One single bad decision. Will you enter?

House rules | Defeat a foe in combat without killing him

Sometimes you want to immobilize, incapacitate or somehow defeat a foe in combat but you don’t want to kill him, and some games add complex mechanics to do that, while other doen’t add any mechanics at all.

Here’s an easy way:

  1. State your intention. “I want to immobilize him but not killing him”.
  2. Attack the enemy as normal, using non-lethal weapons or no weapons at all (punches and kicks might deal anything between a single point of damage to 1d4). When the target reaches zero or less hp, he’s defeated and you achieved what you intended to do.

If mid-combat you decide to try it, and the enemy has suffered damage from lethal weapons, you must use non-lethal weapons or your own hands from now on. But if the target reaches negative hit points, he’s dead, he only survives if he reaches exactly zero (then it’s a good thing to make punches and kicks deal only one point of damage, right?)

Of course, if you want to immobilize him so your friends can kill him, you have to use whatever grapple rules you have.

If you really need more complex rules that these, you know where to find your path to them, if you know what I mean.

Emmy Allen’s Esoteric Enterprises, a first approach

Note: This is not as much a review as it is an abstract of my first impressions after having read the entire game, and some recollections of the original blog entries. Also, I’m writing directly on English, not in Spanish and then translating. I thought it was important to mention it.

Esoteric Enterprises (EE) is the brand new offering by Emmy Allen (of The Gardens of Ynn, The Stygian Library, and Wolf-Packs & Winter Snow fame), and none of the hottest titles out there right now (seriously, go get it!)

EE is a game about “the underworlds of organised crime and the esoteric”; setting-wise, it’s similar to some World of Darkness universes, to wit, Orpheus and Hunter the Vigil (as Emmy states on the introduction,) but also Unknown Armies. This means it’s a game set in the modern day world, but also that the world, although similar to ours, it’s not exactly the same; in the game world there are monsters, magick, and weird things, like some Lovecraftian creatures, a few Changeling the Dreaming things, but most taken from D&D, everything with a dark twist, of course.

System-wise, being part of the Old-School Renaissance, it’s obviously based, at least to some extent, both on Moldvay’s Basic and Cook’s & Marsh’s Expert sets, and also Lamentations of the Flame Princess, to the extent that EE includes LotFP’s streamlined Skill System, with its own set of skills (Charm, Contacts, Forensics, Technology, Vandalism, and several more).

As for its original systems, EE contains a great deal of wounds management: each type caused by bullets and explosives, knives and claws, hammers and punches, fire and acid, electricity and cold weather, poison and diseases. Each type containing their own effects, all horrible and painful (this game is not for the faint of heart: here, some examples: “You’ve been squashed into a pulpy mess, so there’s really barely anything left to bury or reanimate,” “Your organs are shutting down one by one. You’re a Dead Man Walking. Plus, you spend the next round vomiting everywhere, and lose your chance to act”… yes, this is a game where characters die, and easily, unless they are smart).

The are rules for ageing, attribute loss, breaking equipment, cave-ins, escaping bonds, being left alone in the dark, hacking, shape-shifting, drugs, torture, mental damage and a bunch more things. It’s very complete as well as flexible for the referee to implement ad hoc rules when he need resolving something not covered by the book.

Cash & Downtime covers what the characters do in their free time between adventures, and how they spend their gold… I mean, their dollars. There are also systems to manage medical experiments, monsters as player characters (called spooks), spellcasting, running heists, and a great deal of gamemastering information.

One of its best features are the chapters called Rolling up the undercity and Rolling up the occult underworld, which allows you to create the underworld with just a bunch of dice rolls, including locations, tunnels, cults (like the worshippers of Amanita Muscaria, don’t you love it!?), factions and more. Much more.

There are many things I left out, but in conclusion I can say that Esoteric Enterprises is an excellent game and setting, full of ideas. You can run it as body-horror drama, supernatural noir, dark fantasy or urban grimdark. With it, you can run a campaign based on The X-Files, The Invisibles, Neonomicon, Hellblazer, Hellraiser, Buffy the Vampire Slayer, The Lost Boys, Tokyo Gore Police, and some Cronenberg nightmares.

“Are you sure there aren’t any flaws?”

Well, there are a few typos, but nothing too annoying.

“Anything else?”

Well. It’s illustrated with photographs, which are kind of ugly. Remember that cyberpunk game which used photos instead or drawings, and how weird it looked? Well, here happens the same. I would have prefered public domain illustrations, like other of Emmy Allen’s works, but this is not something to hold against the game, let’s be honest and remember that indie games rely heavily on stock art, but you can’t find many modern day stock artwork, so it’s photos.

I have to tell you, though, that despise the pictures, you should try it, it’s a great game and when you are on the table, it’s the emergent story what counts, not the book’s illustrations. Oh! And I made some random tables.

Ugly picture, right?

Old-School Saving Throws Are Rad!

Old-School saving throws tell you against what you are defending; the “how” is left to your imagination.

Like everything in these games, saving throws are a mechanism and not a narrative; the player rolls the dice and the player or referee interprets the result (success or failure) according to the context, or he can ignore the interpretation and it doesn’t matter, the game moves on.

For example, an attack roll doesn’t represent the same in all cases; if successful, it can represent different forms of attack and defense made in a round: thrust, feint, riposte, swing, parry … The important thing is that the dice tell you if you succeed or not, whereas the form of the attack (the “how”) is irrelevant. It’s up to the players to describe it or ignore it and move on with the adventure.

The same applies to saving throws.

While, since 3e, the saving throws tell you the “how” (a reflex save meaning that the character throws himself aside to dodge an attack, a fortitude save meaning the character receives the attack but resists it as would a boxer being punched, a willpower save meaning … well, who knows what the hell it means, that your soul is hard as steel, perhaps?*), old-school saving throws are a mechanic to represent what you are defending against and what are your chances of success, leaving you the responsibility to describe the way your character does it (a responsibility, however, completely negligible).

Thus, we have the 5 categories of old school saving rolls, specifically Basic/Expert Sets (B/X, BECMI), and most OSR retrcolcones, like Labyrinth Lord and Old-School Essentials:

  • Death Ray or Posion
  • Magic Wands
  • Paralysis or Turn to Stone
  • Dragon Breath
  • Rods, Staves or Spells

And these are the categories of AD&D 1e:

  • Paralyzation, Poison or Death Magic
  • Petrification or Polymorph
  • Rod, Staff or Wand
  • Breath Weapon
  • Spell

And, just for fun, those of LotFP:

  • Paralyzation
  • Poison
  • Breath Weapon
  • Magical Device
  • Magic

Although the categories vary from one version to another, the mechanics are identical: you make a saving throw when you are in imminent danger. In normal combat, if an enemy attacks you with his sword, your AC protects you, which not only represents your armor, but also your ability to defend in combat.

But in the face of other dangers, such as a dragon that throws you fire, a basilisk that looks you in the eye, ingesting poison or being the target of a spell (or magic wand), your AC (defense capability plus armor, remember?) does not come into play, but you still have a chance, even if it is small, to avoid damage.

Save Versus Something

Save versus Poison. The adventurer probably did nothing to avoid dying poisoned, the roll is passively successful, the reason he didn’t die can be anything from the poison having no effect or the creature failing to inject it to the adventurer being immune to this specific poison, even divine intervention, or maybe those luminous mushroomes he ate that morning neutralized all toxins.

In 3e, this saving throw would be a fortitude save, and in 5e, a constitution save (which come to be the same, actually). This can only be interpreted in one way: the poison didn’t kill the adventurer due to a powerful immune system.

Of course, the old-school allows this same interpretation, but not only this; it gives you the freedom to interpret the numbers as you see fit.**

Save versus Spells. A damn magic-user attacks you with a fireball. To avoid damage (or, well, half the damage), in 3e or 5e you must make a reflex or dexterity save, meaning that you dodge the fireball (the spell’s description makes this interpretation unlikely, though), but in the old-school we really don’t know how you do it other thank making a save versus Spells (i.e. we only know the mechanic, but we are not offered a narrative interpretation***); maybe the agile thief jumps to the side, yes, but think about that heavy fighter with full armor, can he really dodge? Most likely his armor protects him, but if the idea of a hot metal armor not causing severe damage bothers you, then you can say that he used his sword to deflect the explosion, or he punched the ball of fire like those Dragon Ball fighters do all the time.

Now imagine that you are on a cliff, there is no space to dodge without falling from a great height (and no doubt die), but anyway you make a successful saving throw. Did you dodge the attack? I don’t think so. In the case of a magic-user or an elf, it’s easy to imagine that they know a mystical handsign that works to counter or deflect a spell, reducing (or denying when appropriate) its effectiveness.

The thief and halfling are lucky and that strange, outer, chaotic force known as luck interferes with the spell, reducing its effectiveness. A cleric is protected by his faith (which is another form of magic, or anti-magic if you consider magic as something unholy). The fighter, like the dwarf, relies more on his instinct, his strength, his ability, and in general “sheer defiance”, all of these tangible or demonstrable things, not abstract, philosophical things like magic, and that confidence makes them face magic with disdain, reducing its effectiveness.

* It doesn’t matter, the game moves on.

** Of course you can interpret 3e and 5e saves in any way you see fit.

*** To be honest, 1e offers both a narrative option (“Defensive Adjustment refers to the penalty or bonus applicable to a character’s saving throws against certain forms of attack [such as fire ball, lightning bolts, etc.] due to dodging ability.” PHB, p. 11) and the old-school option (“If some further rationale is needed to explain saving throws versus magic, here is one way of looking at it … A character under magical attack is in a stress situation, and his or her own will force reacts instinctively to protect the character by slightly altering the effects of the magical assault … So a character manages to avoid the full blast of the fireball, or averts his or her gaze from the basilisk or medusa, or the poisonous stinger of the giant scorpion misses or fails somehow to inject its venom. Whatever the rationale, the character is saved to go on.” DMG, p. 81)

Armour Class (AC) Conversion Between OSR/D&D Systems

In this table, you will find the AC values ​​of different editions of Dungeons & Dragons and the most important retroclones/OSR games.

B/X D&D = Dungeons & Dragons Basic/Expert sets. AD&D = Advanced Dungeons & Dragons. BFRPG = Basic Fantasy RPG. S&W = Swords & Wizardry*. BXE = B/X Essentials (name changed to Old-School Essentials). LL = Labyrinth Lord. AS&SH = Astonishing Swordsmen & Sorcerers of Hyperborea. OSRIC = Old School Reference and Index Compilation. DCC = Dungeon Crawl Classics. 1E = Advanced Dungeons & Dragons First Edition. 5E = D&D Fifth Edition. LotFP = Lamentations of the Flame Princess**.

*S&W uses both the descending and ascending systems. In the ascending system, the base AC is 10, and continues identically to DCC, although the armour types are more similar to 1E.

**LotFP has an AC of 18 as the maximum value. This value can increase if you use plate mail with a shield, you have a high dexterity or get circumstantial bonuses.

DCC, 5E, S&W LotFP
(no armor)
(no armor)
(no armor)
(no armor)
(no armor)
(no armor)
(padded leather)
(shield, padded)
(leather armor)
(leather armor)
(studded leather)
(leather, padded)
(leather armor)
(leather armor)
14 6
(scale mail)
(scale mail)
(studded, ring)
(studded, hide)
(chain mail)
(chain mail)
(chain mail)
(scale mail)
(scale mail)
(chain mail)
16 4
(banded mail)
(banded mail)
(chain mail)
(plate mail)
(plate mail)
(plate mail)
(banded armor)
(banded mail)
(plate armor)
18 2 2 3
(plate mail))
19 1 1 2
(field plate)
(full plate)
20 0
(suit armor)
0 1
(full plate)
19 etc.
21 -1 -1 0 20
22 -2 -2 -1 21
23 -3 -3 -2 22
24 -4 -4 -3 23
25 -5 -5 -4 24
26 -6 -6 -5 25

Compatibility between most OSR games, and retro-compatibility with classic D&D editions, are two of their biggest attractions. If you don’t have a manual, you can use the adventures published for it with another system; conversion is easy and in most cases it can be done without prior preparation.