Current ideas:

Potion Effects

Burning while Smited inflicts radiant damage

damage from Plague counts as poison damage

Fires

Scorch Fire is fire and force (flavour text says the fire is magically enchanted) (But scorchfireball charge is fire and acid)
Doom Fire is fire and necrotic
Hell Fire is also fire and necrotic (maybe different dist compared to Doomfire)
Shadowfire maybe just pure necrotic (it does inflict Decay after all)
Icefire (I think that's what it's called) is cold damage
Frostfire is cold damage

Icefire and Frost fire maybe have secondary type depending on what they do and what the flavour text says.

Equipment

Would hopefully be able to use the same system I plan to implement for Tetra and TiC

Only Blade, Axe and Pike slots would contribute to damage distribution