Try to search the encyclopaedia; there you will find what is actually known about it right know.
(rather compicated matter)
in the technical documentation section there, you´ll find sth. about torches and light level. Generally a light spell adds to the amount of lumination around the party...read it,
I think it will be likely that there is no "constant damage" value and even if so it would not be very useful.
The reason, different creatures take less or more damage from spells (&weapons) . There is armor, health, magic resistance (plus some random elements??)and so forth...
For instance a Stone Golem takes different damage from a strong fireball than a screamer does.
some monsters take no damage from spells. Even the effect on the party is not constant.(except for poison maybe)
Imagine that Wisdom might have effect on the spell damage (each champion has different wisdom) and maybe the wizard or priest level or even a hidden skill play a role, et cetera.
there is also a decrease in damage of the spell the farther it travels.(watch a fireball in a long corridor...)so you would even have to write the substraction damage down for each square travelled(more or less)
Maybe there is a default damage. BUt it is ripped out of context...THe only thing you could do is say:
the scorpions in level 10 need around 3 mon fireballs to kill or (a guess) 5-7 "Berserk" hits with a character of [80..84] strength, not wounded and at above 80% stamina value.
Whatever, that´s what i concluded...
