Sakashima, the Face Stealer

Commander ninjutsu {w}{u}{b}
Whenever a Ninja, Spirit, or Rogue you control
deals combat damage to a player, fateseal 1.
You may cast the fatesealed card this turn, and
you may pay mana as though it were mana of
any color to cast it. Otherwise, put that card on
the top or bottom of that opponent's library.
"Punished by the Kami, he is doomed to take
the lives, and the faces, of those he meets."