This seems really fun even though I can't tell if it's good. In EDH I can see Grixis theft decks slotting it right in because it draws, ramps, and even steals!
There's a lot going on here. 7 mana over 2 turns to draw 2 and make a 4/4 flyer might be solid. The issue is it doesn't let you use mana of any color to cast the spells you exile, so you have to generate treasures by attacking or be playing the mirror to use them (or hit spell + a land to cast it). This will feel real bad when you cast the adventure on turn 3, hit two spells you can't cast, and they answer it before it attacks.
That said, card advantage, a solid body and ramp can be good. I think it's likely too weak to see play in standard main decks, but could be a strong play out of the board.
