Enchantment
When Through the Dust enters, it becomes an Aura with enchant creature. Reveal the top seven cards of your library, put a creature card revealed this way onto the battlefield and attach Through the Dust to it. Then put the rest on the bottom of your library in any order. When Through the Dust is no longer on the battlefield, enchanted creature's controller sacrifices it.
Mirage {1}{U}{U}{U} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)