When bullets just aren't enough to fell your foes, it's time to light them up with a dash of magic. Spells are a spectacularly sparkly way to damage your enemies, and have relatively short cooldowns separate from your Fatemaker's chosen Action Skill. Any class can equip any spell that drops as a piece of loot, and you should feel free to swap between spells often to find out which ones work best with your loadout.
Spells have wildly varying properties, even when they're the same basic type such as a fireball, magic missile, summoned hydra, or a gigantic meteor conjured from thin air to rain celestial destruction on your foes. You might find a spell that has multiple charges, allows for continuous casting (perfect for poison beams of death), or resets its own cooldown on a critical hit—and that's just the start. Most spells involve some sort of elemental damage, while others are meant to provide more utility by protecting allies or debuffing enemies, for example.