Popular Entertainer is a rare Legendary Enchantment — Background card from Battle for Baldur's Gate Promos (PCLB), collector number 192s. Current market price: — (foil $0.56), TCGplayer market prices via Scryfall.
Commander creatures you own have "Whenever one or more creatures you control deal combat damage to a player, goad target creature that player controls." (Until your next turn, that creature attacks each combat if able and attacks a player other than you if able.)