There are many schools of spells in iron's spells 'n spellbooks. (fire, ice, nature, etc.)
However, most mobs are not separately weak to fire or resistant to ice, and by default undead are weak to Holy and resistant to Blood, and fire-resistant mobs are resistant to the fire school, but the schools have little significance. This add-on adds one resistance and one vulnerable school to many mod bosses. For example, Ender Dragon is vulnerable to ice and resistant to the End school.
