KMS. U-557, Unlucky U-boat

Deathtouch
Submarine 2 (This creature enters the battlefield
with 2 oxygen counters on it. Remove 1 oxygen
counter: This creature is unblockable this turn)
Whenever KMS. U-557, Unlucky U-boat and at
least one other non-submarine creature you
control attack, sacrifice KMS. U-557, Unlucky
U-boat.