Bontu's Monument + Pitiless Plunderer + Oathsworn Vampire + Altar of Dementia

Bontu's Monument

Pitiless Plunderer

Oathsworn Vampire

Altar of Dementia

How it works

1. Cast Oathsworn Vampire either from your hand or from your graveyard by paying due to Bontu's Monument.
2. Bontu's Monument triggers, causing each opponent to lose 1 life and you to gain 1 life.
3. Activate Altar of Dementia by sacrificing Oathsworn Vampire.
4. When Oathsworn Vampire dies, Pitiless Plunderer triggers, creating a Treasure artifact token.
5. Resolve the Altar of Dementia ability, causing target player to mill cards equal to Oathsworn Vampire's power.
6. Activate the Treasure by tapping and sacrificing it, adding .
7. Repeat.

This clever loop feeds on itself by turning the life you gain into the exact fuel you need to keep going. When you sacrifice Oathsworn Vampire to Altar of Dementia, Pitiless Plunderer steps in to generate a Treasure token upon that death, which you then sacrifice for the black mana required to recast the vampire from your graveyard. That resurrection is made possible because Bontu's Monument quietly provides both a crucial cost reduction to make the spell affordable and the life gain trigger that unlocks Oathsworn Vampire's graveyard-casting condition in the first place.