Lord Xander, the Collector is a mythic Legendary Creature — Vampire Demon Noble card from Streets of New Capenna Promos (PSNC), collector number 197p. Current market price: $4.00 (foil $2.70), TCGplayer market prices via Scryfall.
When Lord Xander enters, target opponent discards half the cards in their hand, rounded down. Whenever Lord Xander attacks, defending player mills half their library, rounded down. When Lord Xander dies, target opponent sacrifices half the nonland permanents they control of their choice, rounded down.