You can harness any of your unspent magical energy to become a deadly flame.
Benefit: By sacrificing an uncast spell or unused spell per day (for spontaneous casters), you can make a ranged touch attack against a single target which deals 1d6 damage per level of the spell sacrificed. This attack counts as a ray and deals fire damage. This ability takes a standard action, and you may use it a number of times per day equal to one half of your mystic theurge level. If the spell sacrificed was a divination spell you had prepared, it deals an additional +1 point of damage per level of the spell sacrificed.
Undefeatable: The Collected Feats Sourcebook, Copyright 2009 – 2010, Louis Porter Jr. Design, Inc. Undefeated, Copyright 2011, Louis Porter Jr. Design, Inc.