Black Widow, Peerless Spy

Skulk, flash, shroud
When Black Widow, Peerless Spy enters the battlefield, detain target creature an opponent controls.
You may exert Black Widow, Peerless Spy if it
has dealt combat damage to a player. When you
do, target player discards a card and you draw a
card. (An exerted creature won't untap during your
next untap step.)