Deflection

Momentum Power
At-Will (once per round)
Action: 
Interrupt action; you must spend your momentum
Trigger: 
A melee attack misses you.
Effect: 

The attack hits a different enemy you are engaged with instead, but deals only half damage.

Adventurer Feat: 

The power also triggers on a ranged attack against AC.

Champion Feat: 

The deflected attack now deals full damage instead of half damage.

Epic Feat: 

Using deflection no longer spends your momentum.