Gnarlroot Trapper is a uncommon Creature — Elf Druid card from Magic Origins (ORI), collector number 100. Current market price: $0.32 (foil $2.11), TCGplayer market prices via Scryfall.
{T}, Pay 1 life: Add {G}. Spend this mana only to cast an Elf creature spell. {T}: Target attacking Elf you control gains deathtouch until end of turn. (Any amount of damage it deals to a creature is enough to destroy it.)