Lavarush Charger

Lavarush Charger costs {1} less to cast for each Mountain card in your graveyard.
When Lavarush Charger enters the battlefield, you may sacrifice X Mountains. If
you do, creatures you control get +X/+0 and gain haste until end of turn.
Sacrifice Lavarush Charger: Return all
Mountain cards from your graveyard to your hand.