Activate Krark-Clan Ironworks by sacrificing Breya, adding {C}{C}.
When Breya dies, Nim Deathmantle triggers, causing you to pay {4} to return Breya from your graveyard to the battlefield and attach Nim Deathmantle to it.
When Breya enters, it triggers, creating two artifact creature tokens.
Activate Krark-Clan Ironworks by sacrificing a creature token, adding {C}{C}.
Repeat.

Infinite artifact ETB

Infinite artifact tokens

Infinite colorless mana

Infinite death triggers

Infinite creature ETB

Infinite creature LTB

Infinite creature sacrifice triggers

Infinite creature tokens

Nim Deathmantle

Krark-Clan Ironworks

Breya, Etherium Shaper

Activate Krark-Clan Ironworks by sacrificing Myr Battlesphere, adding {C}{C}.
When Myr Battlesphere dies, Nim Deathmantle triggers, causing you to pay {4} to return Myr Battlesphere from your graveyard to the battlefield and attach Nim Deathmantle to it.
When Myr Battlesphere enters, it triggers, creating four artifact creature tokens.
Activate Krark-Clan Ironworks by sacrificing a creature token, adding {C}{C}.
Repeat.

Myr Battlesphere

Activate Krark-Clan Ironworks by sacrificing Royal Warden, adding {C}{C}.
When Royal Warden dies, Nim Deathmantle triggers, causing you to pay {4} to return Royal Warden from your graveyard to the battlefield and attach Nim Deathmantle to it.
When Royal Warden enters, it triggers, creating two tapped artifact creature tokens.
Activate Krark-Clan Ironworks by sacrificing a creature token, adding {C}{C}.
Repeat.

Infinite tapped artifact tokens

Infinite tapped creature tokens

Royal Warden

Activate Krark-Clan Ironworks by sacrificing Breya's Apprentice, adding {C}{C}.
Breya's Apprentice dies, triggering Nim Deathmantle, causing you to pay {4} to return Breya's Apprentice from your graveyard to the battlefield, and attach Nim Deathmantle to it.
Breya's Apprentice enters the battlefield, creating a 1/1 Thopter artifact creature token.
Activate Krark-Clan Ironworks by sacrificing the Thopter, adding {C}{C}.
Repeat.

Breya's Apprentice

Activate Krark-Clan Ironworks by sacrificing Threefold Thunderhulk, adding {C}{C}.
When Threefold Thunderhulk dies, Nim Deathmantle triggers, returning Threefold Thunderhulk from your graveyard to the battlefield, and attaching Nim Deathmantle to it.
When Threefold Thunderhulk enters the battlefield, it triggers, creating a number of 1/1 Gnome artifact creature tokens equal to its power.
Activate Krark-Clan Ironworks by sacrificing a Gnome, adding {C}{C}.
Repeat.

Infinite +1/+1 counters on a creature

Threefold Thunderhulk

Activate Krark-Clan Ironworks by sacrificing Precursor Golem, adding {C}{C}.
When Precursor Golem dies, Nim Deathmantle triggers, causing you to pay {4} to return Precursor Golem from your graveyard to the battlefield, and attach Nim Deathmantle to it.
When Precursor Golem enters the battlefield, its first ability triggers, creating two 3/3 Golem creature tokens.
Activate Krark-Clan Ironworks by sacrificing a Golem, adding {C}{C}.
Repeat.

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