The Heart of Arctura

The Heart of Arctura enters the battlefield with
X steam counters on it.
At the beginning of your upkeep, double the
number of steam counters on The Heart of
Arctura.
At the beginning of your end step, if The Heart
of Arctura has 250 or more steam counters, you
win the game.
If you were to take damage, remove that many counters from The Heart of Arctura instead.
Finally... Perfection is within reach - King Arcturus