Zabuza, Demon of The Mist

Islandwalk, Skulk, First Strike

Whenever a non-token creature enters the battlefield
under an opponent's control, you can pay {u}. If you
do, create a blue 2/2 water clone creature token with
first strike and skulk.

{1}{u}{u}{t}: Tap target creature an opponent
controls. That creature doesn't become untapped
until Zabuza leaves the battlefield or targets
another creature with this ability.