Activate Halsin by paying {1}, causing a Treasure token to become a 4/4 Bear creature token in addition to its other types until end of turn.
Activate Lightning Greaves' equip ability by paying {0}, attaching it to the Treasure Bear.
Activate the Treasure Bear token by tapping and sacrificing it, adding {1}.
The Treasure Bear dies, triggering Pitiless Plunderer, creating a Treasure token.
Repeat.

Infinite death triggers

Infinite creature LTB

Infinite creature sacrifice triggers

Halsin, Emerald Archdruid

Pitiless Plunderer

Lightning Greaves

Activate Halsin by paying {1}, causing an artifact token you control to become a 4/4 Bear in addition to its other types until end of turn.
Activate Krark-Clan Ironworks by sacrificing the Bear, adding {C}{C}.
When the Bear dies, Nick Valentine triggers, creating a Clue token.
Repeat.

Infinite artifact ETB

Infinite artifact LTB

Infinite artifact sacrifice triggers

Infinite card draw

Infinite colorless mana

Infinite draw triggers

Nick Valentine, Private Eye

Krark-Clan Ironworks

Activate Halsin by paying {1}, causing a Treasure token to become a 4/4 Bear creature token in addition to its other types until end of turn.
Activate the Treasure Bear token by tapping and sacrificing it, adding {1}.
The Treasure Bear dies, triggering Pitiless Plunderer, creating a Treasure token.
Repeat.

Concordant Crossroads

Thousand-Year Elixir

Combos with "Halsin, Emerald Archdruid"