Lanfear, Daughter of the Night

Whenever a nonland permanent an opponent
controls becomes the target of a spell or ability you
control, gain control of that permanent until
Lanfear leaves the battlefield. This ability triggers
only once per turn.

{3}, {t}, Pay 3 life: Target creature's owner draws a
card. If you own that creature, discard a card.
Activate only as a sorcery.