Selvala, Heart of the Wilds is a mythic Legendary Creature — Elf Scout card from Commander Masters (CMM), collector number 681. Current market price: $16.42 (foil $27.55), TCGplayer market prices via Scryfall.
Whenever another creature enters, its controller may draw a card if its power is greater than each other creature's power. {G}, {T}: Add X mana in any combination of colors, where X is the greatest power among creatures you control.