Shen Kenzo, the Winding Blade

Commander ninjutsu {1}{u/b}{u/b} ({1}{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.)
Creature cards in your hand have ninjutsu
{x}{u/b}{u/b}, where X is that creature's converted
mana cost minus three.
Shen Kenzo, the Winding Blade can't be blocked.