Kossolax, The Forsworn

Mount up {2}{r} (You may cast this card converted
for {2}{r})
Double strike, haste
At the beginning of each opponent's upkeep, you
may have that player gain control of Kossolax
until end of turn. If you do, untap Kossolax, goad
it, and it can't be sacrificed this turn. If you
don't, convert it.