Damage Types & Mechanics

So; several damage types. Off the top of my head, poison, fire, cold, flux, certainly others besides.

Each applies its base damage on hit. For some, that'll be a variable (dmg:fire(1d6)), for some, it'll be set (dmg:fire(3)).

In many cases, there's a secondary effect; being set on fire, taking damage over time from poison, getting frozen, etc.

Some will have cumulative effect (the more fire damage you take, the more likely you are to be set on fire), some will have diminishing returns (cold and poison, where each successive hit within a time period causes less and less damage).

So:

Poison - diminishing returns (successive hits within fifteen seconds cause n-(qty of prior hits) damage, but add n-(qty of prior hits) to the additive hit), additive hit fifteen seconds after first application.
Fire - cumulative, if total of damage taken across ten seconds exceeds (END-6) (if wearing flammable gear / fur / whatever) or (END) (if not wearing anything flammable), target is on fire, and takes the threshold qty of fire damage + 1d6 ten seconds after the threshold was met.
Cold - diminishing returns; successive hits within fifteen seconds cause n-(qty of prior hits) damage.

.... Sod all that for a lark. This isn't simplicity during play; this is onerous. Let's give it a skip.

All damage types are... just damage types. They deal x extra damage, of that type. If you have resistance or armor which guards / soaks that type, yay, otherwise, it's damage, pure and simple.

Modification: they do specific stat damage. Normal damage,  you get to spread across str/dex/end; for the special damage types:

dmg:fire - this damage goes directly to str
dmg:cold - dex
dmg:poison - end
dmg:flux - str/dex
dmg:somethingelse - dex/end
etc.

Simple, and still expresses what they do, to a degree.

(Do I still want to be able to set things alight?)