You demonstrate your skills of mimicry as you perfectly imitate your ally's attack.

Daily  
Standard Action      Personal

Requirement: You must use this power at the end of an extended rest.

Effect: Until the end of your next extended rest, you can use an ally's class or paragon path encounter attack power of 11th level or lower as if it were your paragon path encounter attack power. The ally whose power you gain must be present during the entire extended rest before you use this power. You can use your Charisma for the attack roll and damage roll instead of the ability scores normally associated with that power's attack rolls and damage rolls. You do not need to meet the normal prerequisites to use the power, but you must meet any of its requirements.

Published in Eberron Player's Guide, page(s) 60.