Fraying Sanity is a rare Enchantment — Aura Curse card from Wilds of Eldraine: Enchanting Tales (WOT), collector number 19. Current market price: $0.62 (foil $1.07), TCGplayer market prices via Scryfall.
Enchant player At the beginning of each end step, enchanted player mills X cards, where X is the number of cards put into their graveyard from anywhere this turn.