Tinybones Joins Up is a rare Legendary Enchantment card from Outlaws of Thunder Junction Promos (POTJ), collector number 108p. Current market price: $1.12 (foil $1.04), TCGplayer market prices via Scryfall.
When Tinybones Joins Up enters, any number of target players each discard a card. Whenever a legendary creature you control enters, any number of target players each mill a card and lose 1 life.