Surtr, Guardian of Muspelheim

At the beginning of your end step, you may exile
Surtr. At the beginning of your upkeep, if Surtr
is in exile, you may put it on the battlefield, if
you don't, put a fire counter on it. When Surtr
has 3 or more fire counters on it, return Surtr to
the battlefield and remove all fire counters on it
and it deals three times X damage up to three
other targets where X is the number of fire
counters removed from Surtr this way.