You can cause your arcane strike to be more powerful by expending magical energy.
Benefit: When you use Arcane Strike, you may choose to expend an uncast spell or spell slot (for spontaneous casters) in order to deal more damage with your attacks. Your attacks deal an additional +1 damage per level of the spell you expended. You can use this ability once per day per level of eldritch knight you possess.
Undefeatable: The Collected Feats Sourcebook, Copyright 2009 – 2010, Louis Porter Jr. Design, Inc. Undefeated, Copyright 2011, Louis Porter Jr. Design, Inc.