Activate Goblin Welder by tapping it, causing you to sacrifice the artifact with mana value 0 and return Skull of Ramos from your graveyard to the battlefield.
Scrap Trawler triggers, returning nothing to your hand.
Activate Skull of Ramos by sacrificing it.
Scrap Trawler triggers, returning the artifact with mana value 0 from your graveyard to your hand.
Cast the artifact with mana value 0 by paying {0}.
Mirran Spy triggers, untapping Goblin Welder.
Repeat.

Infinite black mana

Infinite storm count

Artifact with MV = 0

Goblin Welder

Scrap Trawler

Mirran Spy

Skull of Ramos

Cast Skull of Ramos by paying its mana cost.
When Skull of Ramos enters, Retreat to Emeria triggers, creating a 1/1 Kor Ally creature token.
When the Kor Ally enters, Haru triggers, earthbending Skull of Ramos.
Activate Skull of Ramos by sacrificing it.
Haru triggers, returning Skull of Ramos from your graveyard to the battlefield.
Repeat from step 2.

Infinite ETB

Infinite creature tokens

Infinite landfall triggers

Toph, the First Metalbender

Retreat to Emeria

Haru, Hidden Talent

Activate Skull of Ramos by sacrificing it, adding {B}.
Activate Arcbound Reclaimer by removing a +1/+1 counter from it, putting Skull of Ramos from your graveyard onto the top of your library.
Activate Oracle's Vault's second ability by tapping it, exiling Skull of Ramos from the top of your library with the ability to play it until end of turn without playing its mana cost.
Cast Skull of Ramos from exile without paying its mana cost.
Rocco's second ability triggers, putting a +1/+1 counter on Arcbound Reclaimer and creating a Food token.
Activate Clock of Omens by tapping the Food and Skull of Ramos, untapping Oracle's Vault.
Repeat.

Combos with "Skull of Ramos"