Magery spell damage is calculated using the following formulas in the order listed.
The value of DAMAGE SCALAR after these calculations determines how much damage a player or human NPC character can inflict with damaging spells such as Explosion, Energy Bolt, Magic Arrow, etc...
Eval Int vs Magic Resist
If the CASTER'S Evaluate Intelligence skill is higher than the TARGET'S Magic Resist skill then DAMAGE SCALAR = (1.0 + ((CASTER EVAL - TARGET RESIST) / 500.0)
Otherwise, if the TARGET'S Resist skill is higher than the CASTER'S Eval skill then DAMAGE SCALAR = (1.0 + ((CASTER EVAL - TARGET RESIST) / 200.0)
If the CASTER'S Inscription skill is equal to 100.0, and their Tactics and Alchemy skills are both less than or equal to 30.0 skill, then DAMAGE SCALAR + 5% bonus.
Magery Damage Calculation
The DAMAGE SCALAR is then adjusted based on the CASTER'S Magery skill level. -25% damage penalty at 0.0 Magery, increasing to full damage (0% penalty) at 100.0 skill.
Double Damage To Monsters
If the TARGET is neither a player character nor a human NPC then DAMAGE SCALAR x 2.