A quick-and-dirty method of handling poison and venom: Poison and venom do damage based on dungeon level or monster hit dice and have a delay of 1d6 turns for poison, 2d6 turns for venom, adjusted for high Constitution. Damage is halved on a successful save.
More detail, if desired:
Poison is anything artificial (on poison traps and weapons, in poisoned food and drink, etc.) Use dungeon level as poison level. Unless otherwise noted, low-level poisons (dungeon level 1-3) cause damage, high-level poisons (dungeon level 4+) kill.
- Poison Damage = 2 dice per level.
Venom is anything natural (injected by a sting, bite, or claw, or by ingesting a body part.) Use monster hit dice as venom level, with weak venom (monsters with a -1 or more hit point penalty) causing sickness instead, strong venom (monsters with a +1 or more hit point bonus) causing coma.
- Venom Damage = 1 die per venom level.
- Sickness = 1 point per level/hour for 2d6 hours, plus half Move.
- Coma = 1/2 die per level/day for 2d6 days, unable to move or speak.
Delay until poison or venom takes effect is 1d6 turns, 2d6 if poison/venom level <= Constitution. Constitution also affects duration of sickness or coma: if venom level <= Con, the victim gets a second save midway through the illness to shake off the effects early.