Will, Scion of Peace is a mythic Legendary Creature — Human Wizard card from Wilds of Eldraine Promos (PWOE), collector number 218p. Current market price: $1.55 (foil $2.17), TCGplayer market prices via Scryfall.
Vigilance {T}: Spells you cast this turn that are white and/or blue cost {X} less to cast, where X is the amount of life you gained this turn. Activate only as a sorcery.