Matsuri, Incessant Degenerate

Whenever a 1/1 creature enters the battlefield,
you my put Matsuri into the battlefield from
your hand, graveyard or from exile tapped.
You may exert Matsuri as it attacks. When you
do, gain control of target 1/1 creature defending
player controls. (An exerted creature won't untap
during your next untap step.)