Fraying Sanity is a rare Enchantment — Aura Curse card from Hour of Devastation Promos (PHOU), collector number 35s. Current market price: — (foil $3.65), 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.