Jetmir, Nexus of Revels is a mythic Legendary Creature — Cat Demon card from Streets of New Capenna Promos (PSNC), collector number 193p. Current market price: $9.26 (foil $11.56), TCGplayer market prices via Scryfall.
Creatures you control get +1/+0 and have vigilance as long as you control three or more creatures. Creatures you control also get +1/+0 and have trample as long as you control six or more creatures. Creatures you control also get +1/+0 and have double strike as long as you control nine or more creatures.