Sorcerous Origins: The Spellthief

Not every aspiring spellcaster can afford fancy books and powerful mentors, some need to scrape by with whatever knowledge they can gain for themselves. Others that walk this path had all the priveleges in the world, and even more skill, but get bored and choose a more selfish path. Whatever the reason, Spellthieves are some of the most skilled spellcasters, as they can learn spells on a whim and even absorb and reflect spells on their users.

Troublemaker

At 1st level, you are proficient with the shortsword, the scimitar, the rapier, the whip, and the hand crossbow. You also become proficient in light armor.

Steal Spell

At 1st level, you are able to tap into the arcane knowledge of spellcasters nearby you and even rob them of their abilities. If you have advantage on an attack roll against any creature able to cast spells you are able to steal one of their spells and hold onto the ability to cast it until you use this feature again. While you hold their spell, they lose the ability to cast the spell; they regain this ability should you use this feature to steal a new spell.

The spell you steal need not be part of your sorcerer spell list, but every time you cast the stolen spell, you expend a Spell Slot as normal. You use Charisma as your spellcasting ability modifier and your own Spell Save DCs no matter the spell you cast with this feature. You may use any metamagic effect in tandem with the stolen spell.

You don’t need advantage on the attack roll if another enemy of the target is within 5 feet of it, that enemy isn’t incapacitated, and you don’t have disadvantage on the attack roll.

You can not use this feature to steal cantrips from a creature. The level of spell you can steal increases as you gain levels in sorcerer, based on the highest spell slot you can cast. (Ex. A 5th level Sorcerer could steal a 1st, 2nd, or 3rd level spell from their victims, but not a 4th level spell or anything more powerful.)

Absorb Spell

At 6th level, a spellthief becomes more proficient with the stealing spells and may even steal spells being used on himself. When targeted by a spell, the spellthief may expend a reaction and a number of sorcery points equal to double the spell's level. Upon doing this, the spell is absorbed and stolen by the spellthief, replacing whatever spell he may have stolen prior to using this feature and negating the spell's effect on the spellthief.

Should the spell targetting the spellthief have multiple targets, the other targets are affected as normal, but the caster it is stolen from cannot cast it again nor concentrate to maintain the spell. Should the spell be targetting an area that the spellthief is occupying, the entire spell is drawn into the spellthief and negated. (A fireball spell stolen through this method would not deal damage to anyone caught in its area of effect, including the spellthief.)

At 15th the spellthief may cast the stolen spell as part of the reaction used to absorb it, effectively reflecting it at the original caster or any other target of their choice.

Arcane Sight

The spellthief becomes a master at following the sources and signatures of magic, and can track down mages with startling precision. At 14th level, the spellthief may use a bonus action to cast an augmented form of Detect Magic, which does not require concentration and is centered entirely on their line of sight. In addition to learning the school of magic that the spell originates from, the spellthief becomes aware if the spell was casted through arcane or divine means. Should the spellthief spend an action to concentrate on any creature while this ability is active, they may determine if the creature has the ability to cast spells, and the highest level spell slot the creature is able to cast. Arcane sight lasts for 10 minutes, or until the spellthief uses a bonus action to dismiss it.

The spellthief must finish a short rest before using this feature again.

Master Caster

At 18th level, the spellthief becomes so skilled at stealing spells, they no longer require as much of his own power to cast. Whenever using the Steal Spell or the Absorb Spell features to steal a spell, the spellthief no longer must expend a spell slot to cast the stolen spell. Instead, the spellthief may choose to expend a number of sorcery points equal to the spell's level. The spellthief may not use this feature to cast spells from their own store of Sorcerer Spells.