Laughing Jasper Flint is a rare Legendary Creature — Lizard Rogue card from Outlaws of Thunder Junction (OTJ), collector number 355. Current market price: $1.98 (foil $2.30), TCGplayer market prices via Scryfall.
Creatures you control but don't own are Mercenaries in addition to their other types. At the beginning of your upkeep, exile the top X cards of target opponent's library, where X is the number of outlaws you control. Until end of turn, you may cast spells from among those cards, and mana of any type can be spent to cast those spells.