Strefan, Maurer Progenitor is a mythic Legendary Creature — Vampire Noble card from Crimson Vow Commander (VOC), collector number 40. Current market price: $3.71, TCGplayer market prices via Scryfall.
Flying At the beginning of your end step, create a Blood token for each player who lost life this turn. Whenever Strefan attacks, you may sacrifice two Blood tokens. If you do, you may put a Vampire card from your hand onto the battlefield tapped and attacking. It gains indestructible until end of turn.