Casey & Raph, Hotheads + Mortuary + Carrion Feeder

How it works

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Cast Casey & Raph by paying .
When Casey & Raph enters, it triggers. Choose its first mode targeting yourself.
Holding priority, activate Carrion Feeder by sacrificing Casey & Raph.
When Casey & Raph dies, Mortuary triggers, putting Casey & Raph onto the top of your library from your graveyard.
Resolve the Carrion Feeder ability.
Resolve the Casey & Raph trigger from step 2, causing you to exile Casey & Raph from the top of your ability with the ability to cast it from exile without paying its mana cost.
Cast Casey & Raph from exile without paying its mana cost.
Repeat from step 2.

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

1–2 · Exhibition & Core

Allowed in this bracket.

3 · Upgraded

Allowed in this bracket.

4–5 · Optimized & cEDH

All combos are allowed.