Optional Rules
These rules are not required to be used to play this game, and can't come up without being deliberately integrated into your game, and are therefor optional. Technically, by this metric, skills are also Optional Rules. Some of these rules are Recommended, indicating that they are required to be used for the full 'developer intended' play experience (they're the ones I use that I think other people will pretty unanimously like) but you should play however you want to play, not however I want to play. Optional Rules which are not Recommended are rules which I do not recommend unless you actively want to use them.
Age (Recommended)
Minor stat modifications represented by different stages of a creature's life.
Interests (Recommended)
What your character is good at and interested in which doesn't have to do with violence. What other games may call "Skill Checks".
Races (Recommended)
The in-world term used to describe what sort of creature you are. In this fictional world, each Race has its own skills and innate strengths.
Disadvantages
Fears, faults, and failings. When a player encounters one, they are rewarded with +1 Exertion Die (up to their maximum) the next time they wake up.
Experience
A numerical system a Host may choose to use if they are having difficulties determining when players should level up.