Lava Dart is a common Instant card from Modern Horizons (MH1), collector number 134. Current market price: $0.94 (foil $8.66), TCGplayer market prices via Scryfall.
Lava Dart deals 1 damage to any target. Flashback—Sacrifice a Mountain. (You may cast this card from your graveyard for its flashback cost. Then exile it.)