Ruins of Velhmor

Ruins of Velhmor enters the battlefield with twenty mystery counters on it.
At the beginning of your first main phase, you may tap a creature you control, if you do, remove X mystery counters from Ruins of Velhmor where X is the that creature's toughness.
When Ruins of Velhmor have no mystery counters on it, transform it into Meganiar of Velhmor.