Vadrik, Astral Archmage is a rare Legendary Creature — Human Wizard card from Innistrad: Midnight Hunt (MID), collector number 325. Current market price: $0.26 (foil $0.39), TCGplayer market prices via Scryfall.
If it's neither day nor night, it becomes day as Vadrik enters. Instant and sorcery spells you cast cost {X} less to cast, where X is Vadrik's power. Whenever day becomes night or night becomes day, put a +1/+1 counter on Vadrik.