The book itself isn't terribly specific about this, and I can't seem to find any examples of a general spell with a specific level for reference. Do I only use the base of the spell when calculating effect, or do I add in modifiers like targets, duration, range, and requisites when calculating effect? More specifically, if I were to learn the Perdo Vim spell Demon's Eternal Oblivion at level 20, would it reduce a demon's Might by 20 or 30 points?
Reduce a target's Might Score by the level of the spell + 10, as long as the spell penetrates the creature's resistance.
This is the general effect listed, for reference.