Ibiskhan, the Revolting Blaze

Creatures you control but don't own have, "You
may exert this creature as it attacks. When you do,
choose menace, indestructible, or double strike at
random. This creature gains that ability until end
of turn." (If another player gains control of exerted
creature, it will untap during their untap step.)

Whenever you exert a creature, exile the top card
of target opponent's library. Until the end of your
next turn, you may play that card, and mana of
any type can be spent to cast