Activate Viscera Seer by sacrificing Arcbound Prototype.
When Arcbound Prototype dies, its modular ability and persist ability trigger.
Resolve the modular trigger, putting Arcbound Prototype's +1/+1 counters on another artifact creature.
Resolve the persist trigger, returning Arcbound Prototype from your graveyard to the battlefield. It will not have a -1/-1 counter on it due to its modular ability.
Resolve the Viscera Seer ability.
Repeat.

Infinite LTB

Infinite ETB

Infinite sacrifice triggers

Infinite death triggers

Infinite scry 1

Infinite +1/+1 counters on certain creatures

Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight

Viscera Seer

Arcbound Prototype

Activate Antler Skulkin by paying {2}, giving Arcbound Prototype persist until end of turn.
Activate Ashnod's Altar by sacrificing Arcbound Prototype, adding {C}{C}.
When Arcbound Prototype dies, its modular and persist abilities trigger.
Resolve the modular trigger, putting all +1/+1 counters on Arcbound Prototype onto another artifact creature you control.
Resolve the persist trigger, returning Arcbound Prototype from your graveyard to the battlefield with one +1/+1 counter on it due to its modular ability.
Repeat.

Antler Skulkin

Ashnod's Altar

Activate Antler Skulkin by paying {2}, giving Arcbound Prototype persist until end of turn.
Activate Krark-Clan Ironworks by sacrificing Arcbound Prototype, adding {C}{C}.
When Arcbound Prototype dies, its modular and persist abilities trigger.
Resolve the modular trigger, putting all +1/+1 counters on Arcbound Prototype onto another artifact creature you control.
Resolve the persist trigger, returning Arcbound Prototype from your graveyard to the battlefield with one +1/+1 counter on it due to its modular ability.
Repeat.

Krark-Clan Ironworks

Activate Arcbound Prototype by paying {1}{U}, blinking it.
Arcbound Prototype leaves and reenters the battlefield, causing it to enter with +1/+1 counters due to its modular ability, and triggering The Ooze and Deadeye Navigator's soulbond ability.
Resolve Deadeye Navigator's trigger, repairing it and Arcbound Prototype
Resolve The Ooze's trigger, creating a Mutagen token for each +1/+1 counter that was on Arcbound Prototype when it left the battlefield.
Activate Urza's first ability twice by tapping Arcbound Prototype and a Mutagen, adding {U}{U}.
Repeat.

Combos with "Arcbound Prototype"