Activate Ashnod's Altar by sacrificing Breya's Apprentice, adding {C}{C}.
When Breya's Apprentice dies, Nim Deathmantle triggers, causing you to pay {4} to return Breya's Apprentice from your graveyard to the battlefield and attach Nim Deathmantle to it.
When Breya's Apprentice enters, it triggers, creating a creature token.
Activate Ashnod's Altar by sacrificing a creature token, adding {C}{C}.
Repeat.

Infinite death triggers

Infinite creature ETB

Infinite creature LTB

Infinite creature sacrifice triggers

Nim Deathmantle

Ashnod's Altar

Breya's Apprentice

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.

Krark-Clan Ironworks

Activate Breya's Apprentice by paying {1}{U}, blinking it.
When Breya's Apprentice enters the battlefield, it and Deadeye Navigator's soulbond ability trigger.
Resolve the Deadeye Navigator trigger, repairing it and Breya's Apprentice
Resolve the Breya's Apprentice trigger, creating an artifact token.
Activate Urza's first ability twice by tapping Breya's Apprentice and another artifact, adding {U}{U}.
Repeat.

Infinite artifact ETB

Infinite artifact LTB

Infinite tapped artifact tokens

Urza, Lord High Artificer

Deadeye Navigator

Activate Breya's Apprentice by tapping it and sacrificing Lesser Masticore.
When Lesser Masticore dies, its persist ability and Dross Scorpion trigger.
Resolve the Dross Scorpion trigger, untapping Breya's Apprentice.
Resolve the Lesser Masticore trigger, returning it from your graveyard to the battlefield with no -1/-1 counters on it due to Vizier of Remedies.
Resolve the Breya's Apprentice ability, either giving target creature +2/+0 until end of turn, or exiling the top card of your library with the ability to play it until the end of your next turn.
Repeat.

Combos with "Breya's Apprentice"