With the SI Fixes mod, many of the spell mantras are supposed to be changed, and the "Fire Snake" spell is supposed to work.
I have the latest version of Exult and SI Fixes, and the incorrect spells all still say "Ex Por", and "Fire Snake" doesn't work at all, just eating up mana and reagents.
Attached is the best savegame, you can literally try this anywhere.
with the correct SI fixes, this should work