Thraxes, the Molten Fury

Flying
Monstrosity {x}{x}{r} (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)
When Thraxes becomes monstrous, deal X damage to target player and each creature that player controls. Thraxes gains "Sacrifice four mountains: Return Thraxes from your graveyard to the battlefield."