Ashiok, Nightmare Muse is a mythic Legendary Planeswalker — Ashiok card from Theros Beyond Death (THB), collector number 256. Current market price: $3.27 (foil $4.84), TCGplayer market prices via Scryfall.
+1: Create a 2/3 blue and black Nightmare creature token with "Whenever this token attacks or blocks, each opponent exiles the top two cards of their library." −3: Return target nonland permanent to its owner's hand, then that player exiles a card from their hand. −7: You may cast up to three spells from among face-up cards your opponents own from exile without paying their mana costs.