Rhaegal Jadescale

Flying
Whenever Rhaegal Jadescale deals combat
damage to a player, you may pay {2}{u} If you
do, exile the top card of your library face down.
You may look at that card for as long as it
remains exiled. You may play that card without
paying its mana cost for as long as Rhaegal
Jadescale remains on the battlefield.