Tomb of Horrors Adventurer is a rare Creature — Elf Monk card from Battle for Baldur's Gate Promos (PCLB), collector number 100s. Current market price: — (foil $1.94), TCGplayer market prices via Scryfall.
When this creature enters, you take the initiative. Whenever you cast your second spell each turn, copy it. If you've completed a dungeon, copy that spell twice instead. You may choose new targets for the copies. (A copy of a permanent spell becomes a token.)