Traptrix Myrmeleo

Haste
If you haven't yet cast a creature this turn, you
may cast this creature at no mana cost. If you do,
you can't cast another creature this turn except
by card effects (this isn't a card effect). When this
creature enters the battlefield, add 1 "trap hole"
instant from your library to your hand. If this
creature was cast by a card effect, destroy 1 target
non-land/creature permanent your opponent
controls.