Throne of Bones

When Throne of Bones enters the battlefield, you
may gain control of target creature until end of
turn. Untap that creature. It gains haste until end
of turn.
At the end of combat on your turn you may sacrifice a creature. If you do, put a bone counter
on Throne of Bones.
Remove four bone counters from Throne of
Bones: Exile Throne of Bones, then return it to
the battlefield under your control at the
beginning of your next upkeep.