Alkali, the Rouge Assassin

Akali has shroud as long as Akali is untapped.
When Akali enters the battlefield, you may have
it deal damage equal its power to target tapped creature you don't control.
Whenever Akali deals combat damage to a player,
exile target creature that player controls and put
a hit counter on that card. That player loses the
game if they own three or more exiled cards with
hit counters on them. Akali's owner shuffles
Akali into their library.