School of the Spellthief

Even after a lifetime of study, some spells lie forever out of the grasp of wizards. Most wizards make peace with this fact of existence. Others are willing to do anything to obtain the secrets of other spellcasters. They adopt the methods of the criminal underworld, and becomes Spellthieves. Through study and subterfuge in equal measure, they can steal spells and fire them back at their casters. The finest Spellthieves can even pluck a spell from the mind of their opponent and add it to their spellbook.

Spellthief's Calling

Your practice in the usurpation of spells encourages a lifestyle of skulking and deft work. When you choose this tradition at 2nd level, you gain proficiency in the Stealth skill and Thieves' Tools.

Spell Inquisition

Starting at 2nd level, you can prepare yourself to adapt to unfamiliar styles of spellcasting, analyzing enemy incantations and somatic gestures. When a hostile creature you can see or hear within 60 feet of you casts a spell, you may use your reaction to identify the spell by making an Intelligence (Arcana) check. The DC of the check equals 12+the spell's level. On a success, you gain advantage on saving throws against that spell, and attack rolls made with that spell have disadvantage when targeting you. This benefit lasts for ten minutes or until you use this feature again.

Spell Acquisition

Starting at 6th level, you learn to foil enemy spells and turn their magic against them. When you successfully negate a spell with Counterspell or Dispel Magic, as part of the action or reaction used to cast the spell, you may expend a spell slot equal to the level of the negated spell to cast it as a wizard spell. This spell cannot have a casting time longer than one action and uses your spellcasting modifier and DC. When you use this feature, you cannot use any spells other than cantrips until the end of your next turn.

Arcane Drain

At 10th level, your ability to steal magic extends to the energy powering magical objects. When you successfully cast Dispel Magic on an object, construct, or magical effect, you regain a spell slot. The spell slot must be of a lower level than you cast Dispel Magic.

Arcane Larceny

At 14th level, you have mastered the art of stealing spells. Whenever you use your Spell Acquisition feature you can instead choose to steal the spell from the caster. If you choose to do so, add the spell to your list of prepared spells. For the next hour, or until you use this feature again, you may cast the spell treating it as a wizard spell and expending spell slots as normal. The caster of the stolen spell is unable to cast that spell until either the hour passes or you use this feature again.