Activate Ashnod's Altar by sacrificing Lingering Tormentor.
When Lingering Tormentor dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
Activate Ashnod's Altar by sacrificing Lingering Tormentor.
When Lingering Tormentor dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
Repeat.

Infinite ETB

Infinite LTB

Infinite colorless mana

Infinite death triggers

Infinite sacrifice triggers

Mikaeus, the Unhallowed

Ashnod's Altar

Lingering Tormentor

Activate Viscera Seer by sacrificing Lingering Tormentor.
When Lingering Tormentor dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
Thran Vigil triggers, putting a +1/+1 counter on Lingering Tormentor.
Resolve the Viscera Seer ability.
Repeat.

Infinite scry 1

Viscera Seer

Thran Vigil

Activate Viscera Seer by sacrificing Lingering Tormentor.
When Lingering Tormentor dies, its persist ability triggers, returning it from your graveyard to the battlefield without a -1/-1 counter on it due to Vizier of Remedies.
Resolve the Viscera Seer ability
Repeat.

Vizier of Remedies

Activate Phyrexian Altar by sacrificing Lingering Tormentor, adding {B/G}.
When Lingering Tormentor dies, its persist ability triggers, returning it to the battlefield from your graveyard with a -1/-1 counter on it.
Activate Quillspike by paying {B/G} and removing the -1/-1 counter from Lingering Tormentor, giving Quillspike +3/+3 until end of turn.
Repeat.

Infinitely large creature until end of turn

Quillspike

Phyrexian Altar

Activate Ashnod's Altar by sacrificing Lingering Tormentor, adding {C}{C}.
Lingering Tormentor dies, triggering its persist ability, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
Activate Slimefoot by paying {4}, creating a 1/1 Saproling creature token.
The Saproling enters the battlefield, triggering Ivy Lane Denizen, putting a +1/+1 counter on Lingering Tormentor.
Activate Ashnod's Altar by sacrificing the Saproling, adding {C}{C}.
The Saproling dies, triggering Slimefoot, dealing 1 damage to each opponent and causing you to gain 1 life.
Repeat.

Infinite damage

Infinite lifegain

Infinite lifegain triggers

Slimefoot, the Stowaway

Ivy Lane Denizen

Activate Kykar by sacrificing Lingering Tormentor, adding {R}.
Lingering Tormentor dies, triggering its persist ability, returning it from your graveyard to the batltefield without a -1/-1 counter on it due to Solemnity.
Repeat.

Combos with "Lingering Tormentor"