Beledros Witherbloom is a mythic Legendary Creature — Elder Dragon card from Strixhaven: School of Mages Promos (PSTX), collector number 163p. Current market price: $8.41 (foil $14.99), TCGplayer market prices via Scryfall.
Flying At the beginning of each upkeep, create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life." Pay 10 life: Untap all lands you control. Activate only once each turn.