Allosaurus Rider is a rare Creature — Elf Warrior card from Duel Decks: Elves vs. Goblins (DD1), collector number 2. Current market price: $5.27, 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.