A spell is a one-time magical effect that come in two types: arcane (cast by bards, sorcerers, wizards, and assassins) and divine (cast by clerics, druids, paladins, rangers, favored souls, spirit shamans and blackguards).

Technically, Blackguards and Assassins do not cast proper spells in NWN2, but have a few feats each which activate a certain spell's power.