Assemble the Players is a rare Enchantment card from Murders at Karlov Manor Promos (PMKM), collector number 3p. Current market price: $0.50 (foil $0.90), TCGplayer market prices via Scryfall.
You may look at the top card of your library any time. Once each turn, you may cast a creature spell with power 2 or less from the top of your library.