Activate Ashnod's Altar by sacrificing Eternal Witness, adding CC.
When Eternal Witness dies, Pitiless Plunderer triggers, creating a Treasure artifact token.
Activate the Treasure by tapping and sacrificing it, adding .
Activate Doomed Necromancer by paying , tapping it and sacrificing it.
When Doomed Necromancer dies, Pitiless Plunderer triggers, creating a Treasure artifact token.
Resolve the Doomed Necromancer ability, returning Eternal Witness from your graveyard to the battlefield.
When Eternal Witness enters the battlefield, it triggers, returning Doomed Necromancer from your graveyard to your hand.
Activate a Treasure by tapping and sacrificing it, adding .
Cast Doomed Necromancer by paying 2.
Repeat.
This clever recycling loop turns the graveyard into an engine by continuously trading creatures back and forth. You use Ashnod's Altar to sacrifice Eternal Witness, which funds Doomed Necromancer's ability—haste provided by Tyvar, Jubilant Brawler lets the Necromancer jump right into action—to pull the Witness back from the graveyard, while the Witness in turn plucks the Necromancer right back to your hand upon entry. Meanwhile, Pitiless Plunderer watches the carnage and quietly mints a Treasure token on every single death to generate the extra black mana needed to keep casting the Necromancer on repeat.