Greninja, Sea Hidden Ninja

If a players declares combat, you may cast
Greninja and have it attack. If yo do so, return
it to your hand at the end of combat.
When Greninja attacks, choose target player or planeswalker. Until end of turn, when Greninja
deals combat damage to that target, put a number of +1/+1 counters on target creature you control
equal to damage Greninja dealt.
Haste, Unblockable