Marwyn, the Nurturer is a rare Legendary Creature — Elf Druid card from Foundations Jumpstart (J25), collector number 687. Current market price: $6.11, TCGplayer market prices via Scryfall.
Whenever another Elf you control enters, put a +1/+1 counter on Marwyn. {T}: Add an amount of {G} equal to Marwyn's power.