Allosaurus Rider is a rare Creature — Elf Warrior card from Coldsnap (CSP), collector number 101. Current market price: $6.28 (foil $18.70), TCGplayer market prices via Scryfall.
You may exile two green cards from your hand rather than pay this spell's mana cost. Allosaurus Rider's power and toughness are each equal to 1 plus the number of lands you control.