Monk's Guide to the Solo Wizard
Mob Resistance to Spells >>>
In general, fire spells have an advantage over animals and undead, and are weak to insects (yeah yeah, I know spiders are technically arachnids, but in DAOC they're insects). Ice spells have an advantage against insects and are weak to animals. Humanoids seems to be a mixed bag: sometimes there'll be a bonus, or penalty, or neither.