Spell Thief

Most wizards spend their lives studying magic, dedicating themselves to one of the eight schools. Others, however, prefer a more pragmatic approach to the arcane arts...

The tradition of the Spell Thief focuses around using the spells of other casters against them. Spell thieves specialize in causing confusion and mischief, and are generally distrusted among practitioners of the more typical schools. Within circles of spell thieves, however, they pride themselves in not being bound by the restrictions of other wizards, due to their ability to adapt on the fly.

Arcane Thievery

Starting at 2nd level, when a creature who is visible to you casts a spell that is on the wizard spell list, you can use your reaction to make an Intelligence (Arcana) check to identify the spell, with a DC of 12 + the spell's level. If you successfully identify it, you can memorize and mimic the verbal, somatic, and material components to the spell. You don't have to make this check if it's an ally you're stealing from.

You can cast this spell as if it was on your spell list, as long as it is of a level that you can prepare. The stolen spell still expends spell slots. You keep this spell memorized until you steal another spell, or until you finish a long rest.

You can steal one additional spell at 6th level, and one more at 14th level. When stealing spells over this limit, you can choose which spell to replace.

You can use this feature a number of times equal to your Intelligence modifier (a minimum of once). You regain any expended uses when you finish a long rest.

Spell Forgery

Also starting at 2nd level, you gain the ability to add spells that you steal to your spellbook. The gold and time you must spend to copy a stolen spell into your spellbook is halved.

Master of Mimicry

At 6th level, your knowledge of mimicry extends to all forms of spells, both arcane and divine. You can now steal spells from any class, although non-wizard spells cannot be added to your spellbook.

Non-wizard spells that you steal use your spellcasting ability to cast, rather than their original spellcasting ability.

Befuddlement

Beginning at 10th level, your ability to mimic spells confuses even the best casters. When you steal a spell, you can choose to deal half your wizard level in psychic damage to the target.

Grand Thievery

At 14th level, you have perfected the art of stealing spells from other casters. You no longer lose any spells you steal after a long rest.