Toph, the First Metalbender + Retreat to Emeria + Haru, Hidden Talent + Skull of Ramos

How it works

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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.

In which brackets is this combo allowed, per Spellbook's Exhibition tier?

1–2 · Exhibition & Core

Allowed in this bracket.

3 · Upgraded

Allowed in this bracket.

4–5 · Optimized & cEDH

All combos are allowed.