Activate Ashnod's Altar by sacrificing Thorin, adding {C}{C}.
When Thorin dies, Nim Deathmantle triggers, causing you to pay {4} to return Thorin from your graveyard to the battlefield and attach Nim Deathmantle to it.
When Thorin enters, it triggers, attaching Nim Deathmantle to Raptor Hatchling, and then having it deal damage to itself.
Raptor Hatchling triggers, creating a creature token.
Activate Ashnod's Altar by sacrificing the creature token, adding {C}{C}.
Repeat.

Infinite creature ETB

Infinite creature LTB

Infinite death triggers

Infinite creature sacrifice triggers

Nim Deathmantle

Ashnod's Altar

Thorin, Mountain-king

Raptor Hatchling

Activate Ashnod's Altar by sacrificing Thorin, adding {C}{C}.
When Thorin dies, Nim Deathmantle triggers, causing you to pay {4} to return Thorin from your graveyard to the battlefield and attach Nim Deathmantle to it.
When Thorin enters, it triggers, attaching Nim Deathmantle to Sporeweb Weaver, and then having it deal damage to itself.
Sporeweb Weaver triggers, creating a creature token and causing you to gain 1 life
Activate Ashnod's Altar by sacrificing the creature token, adding {C}{C}.
Repeat.

Infinite lifegain

Infinite lifegain triggers

Sporeweb Weaver

Activate Ashnod's Altar by sacrificing Thorin, adding {C}{C}.
When Thorin dies, Nim Deathmantle triggers, causing you to pay {4} to return Thorin from your graveyard to the battlefield and attach Nim Deathmantle to it.
When Thorin enters, it triggers, attaching Nim Deathmantle to Polyraptor, and then having it deal damage to itself.
Polyraptor triggers, creating a creature token.
Activate Ashnod's Altar by sacrificing the creature token, adding {C}{C}.
Repeat.

Polyraptor

Activate Ashnod's Altar by sacrificing Thorin, adding {C}{C}.
When Thorin dies, Nim Deathmantle triggers, causing you to pay {4} to return Thorin from your graveyard to the battlefield and attach Nim Deathmantle to it.
When Thorin enters, it triggers, attaching Nim Deathmantle to Overgrown Armasaur, and then having it deal damage to itself.
Overgrown Armasaur triggers, creating a creature token.
Activate Ashnod's Altar by sacrificing the creature token, adding {C}{C}.
Repeat.

Overgrown Armasaur

Activate Ashnod's Altar by sacrificing Thorin, adding {C}{C}.
When Thorin dies, Nim Deathmantle triggers, causing you to pay {4} to return Thorin from your graveyard to the battlefield and attach Nim Deathmantle to it.
When Thorin enters, it triggers, attaching Nim Deathmantle to Vrondiss, and then having it deal damage to itself.
Vrondiss triggers, creating a creature token.
Activate Ashnod's Altar by sacrificing the creature token, adding {C}{C}.
Repeat.

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