Activate Bile Urchin by sacrificing it.
When Bile Urchin dies, Mortuary and Blood Artist trigger.
Resolve the Mortuary trigger, putting Bile Urchin from your graveyard onto the top of your library.
Resolve the Blood Artist trigger, causing you to gain 1 life and target opponent to lose 1 life.
Resolve the Bile Urchin ability.
Cast Bile Urchin 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

Infinite lifeloss

Mortuary

Bile Urchin

Blood Artist

Gwenom, Remorseless

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

Solemnity

Luminous Broodmoth

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

Infinite green mana

Infinite landfall triggers

Zimone, Mystery Unraveler

Yedora, Grave Gardener

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

Gravespawn Sovereign

Intruder Alarm

Activate Bile Urchin by sacrificing it.
Bile Urchin dies, triggering Salvaging Station and Kaya's Ghostform.
Resolve the Salvaging Station trigger, untapping it.
Resolve the Kaya's Ghostform trigger, returning Bile Urchin from your graveyard to the battlefield.
Resolve the Bile Urchin ability from step 1, causing target player to lose 1 life.
Activate Salvaging Station by tapping it, returning Kaya's Ghostform from your graveyard to the battlefield attached to Bile Urchin.
Repeat.

Kaya's Ghostform

Salvaging Station

Encroaching Mycosynth

Cast Bile Urchin by paying its mana cost if it is in your hand. Otherwise, activate Tayam by paying {3} and removing three counters from creatures you control, causing you to mill three cards and return Bile Urchin from your graveyard to the battlefield with a vigilance counter on it.
When Bile Urchin enters the battlefield, Metastatic Evangel triggers, causing you to put a +1/+1 counter on Cryptic Trilobite and Basking Broodscale and a vigilance counter on Bile Urchin.
Basking Broodscale triggers, creating a 0/1 Eldrazi Spawn creature token that enters with a vigilance counter on it.
Activate Cryptic Trilobite by removing a +1/+1 counter from it, adding {C}{C} that can only be spent to activate abilities.
Activate the Eldrazi Spawn by sacrificing it, adding {C}.
Activate Tayam by paying {3}, removing both vigilance counters from Bile Urchin and another counter from a creature you control.
Holding priority, activate Bile Urchin by sacrificing it.
Resolve the Tayam ability, causing you to mill three cards and return Bile Urchin from your graveyard to the battlefield with a vigilance counter on it.
Repeat from step 2.
Repeat.

Combos with "Bile Urchin"