Piper of the Swarm is a rare Creature — Human Warlock card from Throne of Eldraine Promos (PELD), collector number 100p. Current market price: $1.80 (foil $5.55), TCGplayer market prices via Scryfall.
Rats you control have menace. {1}{B}, {T}: Create a 1/1 black Rat creature token. {2}{B}{B}, {T}, Sacrifice three Rats: Gain control of target creature.