Activate Death Cultist by sacrificing it.
When Death Cultist dies, Mortuary triggers, putting Death Cultist from your graveyard onto the top of your library.
Resolve the Death Cultist ability, causing target player to lose 1 life and you to gain 1 life.
Cast Death Cultist from the top of your library by paying 1 life.
Repeat.

Infinite LTB

Infinite ETB

Infinite sacrifice triggers

Infinite death triggers

Infinite lifegain triggers

Infinite storm count

Mortuary

Death Cultist

Gwenom, Remorseless

Activate Death Cultist by sacrificing it, returning it from the battlefield to your hand due to Necromancer Magemark's replacement effect.
Put Glistening Oil into your graveyard, triggering itself, returning it from your graveyard to your hand.
Resolve Death Cultist's ability, causing target player to lose 1 life and you to gain 1 life.
Cast Death Cultist by paying {B/P}.
Aetherflux Reservoir and K'rrik each trigger.
Resolve K'rrik's trigger, putting a +1/+1 counter on it.
Resolve Aetherflux Reservoir's trigger, gaining 1 life for each spell you've cast this turn.
Cast Glistening Oil targeting Death Cultist by paying {B/P}{B/P}.
Aetherflux Reservoir and K'rrik each trigger.
Resolve K'rrik's trigger, putting a +1/+1 counter on it.
Resolve Aetherflux Reservoir's trigger, gaining 1 life for each spell you've cast this turn.
Repeat.

Infinite +1/+1 counters on K'rrik

Infinite damage

Infinite lifegain

Infinite lifeloss

K'rrik, Son of Yawgmoth

Necromancer's Magemark

Glistening Oil

Aetherflux Reservoir

Activate Death Cultist by sacrificing it.
When Death Cultist dies, Luminous Broodmoth triggers, returning Death Cultist from your graveyard to the battlefield without a flying counter on it due to Solemnity.
Resolve the Death Cultist ability.
Repeat.

Solemnity

Luminous Broodmoth

Activate Death Cultist by sacrificing it.
When Death Cultist dies, Yedora triggers, returning Death Cultist from your graveyard to the battlefield face-down as a Forest land.
When Death Cultist enters the battlefield, Zimone triggers.
Holding priority, activate Death Cultist by tapping it, adding {G}.
Resolve the Zimone trigger, turning Death Cultist face-up.
Resolve the Death Cultist ability from step 1.
Repeat.

Infinite green mana

Infinite landfall triggers

Zimone, Mystery Unraveler

Yedora, Grave Gardener

Sacrifice Death Cultist to have target opponent lose 1 life and you gain 1 life.
Tap 5 untapped zombies you control to return Death Cultist to the battlefield.
Intruder Alarm triggers, untapping all creatures.
Repeat.

Gravespawn Sovereign

Intruder Alarm

Combos with "Death Cultist"