Activate Goblin Sledder by sacrificing Putrid Goblin.
When Putrid Goblin dies, its persist ability triggers, returning it from your graveyard to the battlefield without a -1/-1 counter on it due to Metallic Mimic.
Resolve the Goblin Sledder ability.
Repeat.

Infinite creature ETB

Infinite creature LTB

Infinite death triggers

Infinite creature sacrifice triggers

Infinitely large creatures you control until end of turn

Putrid Goblin

Metallic Mimic

Goblin Sledder

Cast First Day of Class by paying {1}{R}
Activate Goblin Sledder by sacrificing Putrid Goblin
When Putrid Goblin dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
When Putrid Goblin enters, First Day of Class triggers, putting a +1/+1 counter on Putrid Goblin.
Resolve the Goblin Sledder ability.
Repeat from step 2

First Day of Class

Cast Doomsday by paying {B}{B}{B}, searching your library and graveyard for one any other card, Zealous Conscripts, Goblin Sledder, Kiki-Jiki, and Priest of Gix, exiling all other cards from your graveyard and library, and then placing the remaining cards on top of your library in the order previously listed and losing half your life, rounded up.
Activate Grenzo by paying {2}, putting Priest of Gix into your graveyard and then onto the battlefield, adding {B}{B}{B}.
Activate Grenzo by paying {2}, putting Kiki-Jiki into your graveyard and then onto the battlefield.
Activate Kiki-Jiki by tapping, creating a token copy of Priest of Gix.
Token copy of Priest of Gix entering the battlefield, adding {B}{B}{B}.
Activate Grenzo by paying {2}, putting Goblin Sledder into your graveyard and then onto the battlefield.
Activate Goblin Sledder by sacrificing it, giving Grenzo +1/+1 until end of turn.
Activate Grenzo by paying {2}, putting Zealous Conscripts into your graveyard and then onto the battlefield, untapping Kiki-Jiki.
Activate Kiki-Jiki by tapping, creating a token copy of Zealous Conscripts.
Repeat from step 8.

Infinite creature tokens with haste

Doomsday

Grenzo, Dungeon Warden

Zealous Conscripts

Kiki-Jiki, Mirror Breaker

Priest of Gix

Activate Goblin Sledder by sacrificing Putrid Goblin
When Putrid Goblin dies, its persist ability triggers, returning it from your graveyard to the battlefield without a -1/-1 counter on it due to Vizier of Remedies.
Resolve the Goblin Sledder ability.
Repeat.

Vizier of Remedies

Combos with "Goblin Sledder"