Downhill Charge 
Instant
You may sacrifice a Mountain rather than pay this spell's mana cost. Target creature gets +X/+0 until end of turn, where X is the number of Mountains you control.
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyLEGALvintageLEGALcommanderLEGAL