Cast Oathsworn Vampire either from your hand or graveyard by paying 1.
Edgar triggers, creating a 1/1 Vampire creature token.
Activate Warren Soultrader by paying 1 life and sacrificing Oathsworn Vampire.
When Oathsworn Vampire dies, Popular Egotist triggers, causing target opponent to lose 1 life and you to gain 1 life.
Resolve the Warren Soultrader ability, creating a Treasure token.
Repeat steps 3 through 5 once, sacrificing the Vampire token instead.
Activate two Treasures by tapping and sacrificing them, adding 1.
Repeat.
This elegant loop turns a simple coven of vampires into an engine of endless drain. Warren Soultrader acts as the sacrificial heart of the operation, turning your creatures into mana and Treasures while feeding Popular Egotist, whose passive trigger ensures that every death drains your opponent and gains you life. That very life-gain is the key that unlocks Oathsworn Vampire, allowing it to crawl endlessly back from the graveyard for just {1}{B}, while Edgar Markov quietly observes from the command zone or battlefield, utilizing his *Eminence* ability to swell your ranks with a fresh 1/1 Vampire token every single time you cast it.