Fuma Kotaro, Master Thief

Ninjutsu {3}{b} ({3}{b}, Return an unblocked attacker
you control to hand: Put this card onto the battlefield
from your hand tapped and attacking.)
Whenever Fuma Kotaro deals combat damage to
a player, exile the top card of each player's library. Until end of turn, you may play one of those
cards. If you cast a spell this way, pay life equal to its mana value rather than paying its mana cost.