Reckless Pyromancer

Whenever another creature enters the battlefield, it gains haste and +X/+X until end of turn where X is the number of mountains on the battlefield.
Overheat {r} ({r}: This creature gets +X/+X where X is the number of Mountains on the battlefield. It does not untap during it's controller's next untap phase.)
All lands are mountains in addition to its other types.