Arel, Unseen Whisperer

Flash
When Arel, Unseen Whisperer is turned face up,
it gains hexproof until end of turn.
Whenever you cast a spell that targets only Arel,
Unseen Whisperer, you may pay {3}. If you do,
exile any number of creatures you control in a
face-down pile, shuffle that pile, then return
those cards to battlefield face-down. (They're 2/2 creatures.)