Halaster Blackcloak

When Halaster Blackcloak enters the battlefield, if you haven't completed Dungeon of the Mad Mage, return Halaster Blackcloak to its owner's hand and venture into the dungeon.
Whenever Halaster Blackcloak attacks, reveal cards from the top of your library until you reveal an instant or sorcery card. You may cast that card without paying its mana cost. Put the rest on the bottom of your librar