Into the Odd is one of the best rules-light* OSR systems in the market, and with good reason.
Warning: If you need the manual to give you the precise instructions to determine if the Player Characters can or can not do something, you most likely won’t like Into the Odd. Chris McDowall, its creator, designed the game for the referees to determine what’s possible in their campaign worlds, and how to resolve every unforeseen situation. It’s a game of imagination and problem solving.
A second warning? Well why not!? This is not a review but a commentary on what I like most about this game and its rules-light approach. If up to this day you don’t have idea what Into the Odd is, I can only refer you to these two reviews:  .
Few and simple rules are a feature, not a flaw. This approach to game design allows the referee to design their own adventures with the necessary freedom to include whatever content they want, either their own or taken from another source. Do you like that RuneQuest Classic Edition adventure where you have to protect a pawnshop from an attack by baboons in alliance with a group of non-human outlaws led by a centaur, but don’t have the time or energy (or interest) to learn the mechanics of the game? Very simple. Convert it! Converting it, even converting it on the fly into playable material for your Into the Odd campaign, is, if not trivial, very easy. Of course you need to familiarize with the original source before you try it.
While Gary Gygax throws a tantrum in his grave every time someone introduces non-AD&D material to his campaign (“[a]dding non-official material puts your game outside the D&D or AD&D game system … [E]xtraneous tinkered material onto the existing D&D or AD&D campaign will quickly bring it to the lower level at best, ruin it at worst.”**), Chris (like most Old-School Renaissance designers) believes that the referee is the only one who can say what is valid in his or her own campaign world. They are right.
This flexibility is what has allowed us to have works like Silent Titans (mini-setting for Into the Odd) and Troika! (a complete game based on Fighting Fantasy), both being works that don’t adhere to the precepts of the well-thinking heads—gamekeepers—who claim authority—albeit false—to say what is valid and what is not valid in the games of others.
This same flexibility is what I have sought to exploit in Goddess of the Crypt, a mini-dungeon that I wrote for Into the Odd which combines Egyptian and Mayan themes (subtle and not so subtle), weird fiction, non-Euclidean geometry and a touch of gonzo oddness.
Using the rules that are included in Into the Odd, it is possible to extrapolate your ideas to create the content you need, or want, and assign ad hoc mechanics to solve the (in-game) conflicts that occur due to the “extraneous material tinkered onto” the game you are playing.
One idea that Into the Odd allowed me to perform better than other systems, was this list of replacement adventurers, useful for those times when you need a new character for a player or want to try a concept different from those included in the book but there’s no time (or energy) to create a new concept.
So, what are you waiting for? If you didn’t abandon this article after the warning, then it would be unfair to not descend into the odd world of this little gem of a game.
*Traditional OSRs, like Labyrinth Lord or Lamentations of the Flame Princess, are not included in my definition of rules-light system even when they’re actually light and easy to learn. In this case, rules-light systems are those that contain their rules in a few pages, have few stats, and minimum bookkeeping.
**Gary could be such an asshole at times.