Thougtstealer

Flying
Voyage — 1{u}, {t}: Exile Thoughtstealer until
the beginning of your next upkeep. When it
returns, target opponent discards a card and you
create a number of Treasure tokens equal to the discarded cards converted mana cost. Activate
this ability only during your turn. (Treasures are artifacts with "{t}, Sacrifice this artifact: Add one
mana of any color.")