Vin, Mistborn Adept

Commander ninjutsu {u}{b} ({u}{b}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand or the command zone tapped and attacking.)
Whenever a Ninja you control deals combat damage to a player, reveal the top card of
your library and put that card into your
hand. Each opponent loses life equal to that card's mana value.