Put a counter on War Elemental.
The Great Goblin's first ability triggers, as War Elemental is a Goblin, Orc and Army due to Stalactite Dagger, dealing 2 damage to an opponent.
War Elemental triggers, putting a +1/+1 counter on it.
Repeat from step 2.

Infinite +1/+1 counters on a creature

Infinite damage

The Great Goblin

War Elemental

Stalactite Dagger

Activate Skirk Prospector by sacrificing it, adding {R}.
When Skirk Prospector dies, The Great Goblin's second ability and Mortuary trigger.
Resolve the Mortuary trigger, putting Skirk Prospector onto the top of your library from your graveyard.
Resolve the Great Goblin trigger, exiling Skirk Prospector from the top of your library with the ability to play it until the end of your next turn.
Cast Skirk Prospector from exile by paying {R}.
Repeat

Infinite ETB

Infinite LTB

Infinite death triggers

Infinite sacrifice triggers

Infinite storm count

Mortuary

Skirk Prospector

Activate Yahenni by sacrificing Impulsive Pilferer
When Impulsive Pilferer dies, it, The Great Goblin's second ability and Mortuary trigger.
Resolve the Impulsive Pilferer trigger, creating a Treasure token.
Resolve the Mortuary trigger, putting Impulsive Pilferer onto the top of your library from your graveyard.
Resolve the Great Goblin trigger, exiling Impulsive Pilferer from the top of your library with the ability to play it until the end of your next turn.
Resolve the Yahenni ability.
Activate the Treasure by tapping and sacrificing it, adding {R}.
Cast Impulsive Pilferer from exile by paying {R}.
Repeat

Impulsive Pilferer

Yahenni, Undying Partisan

Activate Carrion Feeder by sacrificing the Goblin, Orc or Army
When the Goblin, Orc or Army dies, Pitiless Plunderer, The Great Goblin's second ability and Mortuary trigger.
Resolve the Pitiless Plunderer trigger, creating a Treasure token.
Resolve the Mortuary trigger, putting the Goblin, Orc or Army onto the top of your library from your graveyard.
Resolve the Great Goblin trigger, exiling the Goblin, Orc or Army from the top of your library with the ability to play it until the end of your next turn.
Resolve the Carrion Feeder ability
Activate the Treasure by tapping and sacrificing it, adding one mana of any color.
Cast the Goblin, Orc or Army from exile by paying its mana cost.
Repeat

Goblin, Orc or Army Creature Castable for One Colored Mana

Pitiless Plunderer

Carrion Feeder

Activate Umbral Collar Zealot by sacrificing the Goblin, Orc or Army
When the Goblin, Orc or Army dies, The Great Goblin's second ability and Mortuary trigger.
Resolve the Mortuary trigger, putting the Goblin, Orc or Army onto the top of your library from your graveyard.
Resolve the Great Goblin trigger, exiling the Goblin, Orc or Army from the top of your library with the ability to play it until the end of your next turn.
Resolve the Umbral Collar Zealot ability
Cast the Goblin, Orc or Army from exile by paying its mana cost.
The Vision and Scarlet Witch triggers, adding {R} and putting a +1/+1 counter on it
Repeat

Combos with "The Great Goblin"