Yurei, Shrouded in Shadows

Commander Ninjutsu {1}{u}{b}
Shadow-jutsu {1}{u}{b} ({1}{u}{b}, Sacrifice an
unblocked attacker you control: Return this creature
from your graveyard onto the battlefield tapped and
attacking.)
Ninja creature cards in your graveyard have
shadow-jutsu. The shadow-jutsu cost is equal to
its mana cost.