House Rules?

Crypts & Things (in case you didn't know) is based off the excellent "0e" retro-clone Swords & Wizardry. It follows most of the standard "D&D-isms", such as Character Classes, Armor Class, Hit Points, Spell Levels, and so forth. Where it differs is in some of its extra rules and some of its re-interpretations of the existing ones.

Without getting into extensive quoting of the rules, C&T includes some fun stuff like a Luck mechanic, rules for Sanity and Corruption, and some fun tweaks to the standard PC classes. Rather than an attempt to add complexity, the changes add more to the flavor of the game than the mechanics. d101 is after a pretty specific feel here, and while Zarth is a great setting for that kind of pulp swords & sorcery, the game is not "tied" to one setting. A fact I for one appreciate.

I've always been leery of too many house-rules. It can raise the specter of "Why are you playing that game at all?" While I have not used these rules in actual play yet, I can say they seem to flow from a common motivation and thus have a more coherent feel to them than random "patches" stuck on someone's D&D game to assuage players or DMs for perceived mechanical failures.