Celestus Sanctifier is a common Creature — Human Cleric card from Innistrad: Midnight Hunt (MID), collector number 12. Current market price: $0.05 (foil $0.16), TCGplayer market prices via Scryfall.
If it's neither day nor night, it becomes day as this creature enters. Whenever day becomes night or night becomes day, look at the top two cards of your library. Put one of them into your graveyard.