The Mindskinner is a rare Legendary Enchantment Creature — Nightmare card from Duskmourn: House of Horror (DSK), collector number 357. Current market price: $3.52 (foil $5.66), TCGplayer market prices via Scryfall.
The Mindskinner can't be blocked. If a source you control would deal damage to an opponent, prevent that damage and each opponent mills that many cards.