Phantoms of Fymaest

Menace, Reach
When Phantoms of Fymaest attacks, exile the top card of your library face down. Other players may look at that card and must tell you its mana cost. Until end of turn, you may cast that card, and spend mana as though it were mana of any
color to cast it.
When something is lost, the hunters will retrieve it. When something is found, they will kill everyone involved.