Thorin, Mountain-king + Raphael, Ninja Destroyer + Nim Deathmantle + Carrion Feeder

How it works

Activate Carrion Feeder by sacrificing Thorin.
When Thorin dies, Nim Deathmantle triggers, causing you to pay to return Thorin from your graveyard to the battlefield and attach Nim Deathmantle to it.
When Thorin enters, it triggers, attaching Nim Deathmantle to Raphael, and then having Raphael deal 6 damage to itself.
Raphael triggers, adding six .
Resolve the Carrion Feeder ability.
Repeat.

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.