Polemus, the Recruiter

Whenever Polemus, the Recruiter enters the battlefield under it's owner's control, you may exchange control of Polemus, the Recruiter and
target creature an opponent controls. (This effect
lasts indefinitely.)
When Polemus, the Recruiter dies, return it to
it's owner's hand.

"When you arrive, tell them Polemus sent you."
-Polemus