Grub, Storied Matriarch // Grub, Notorious Auntie + Combat Celebrant + Anger

Decks

How it works

Declare Grub and Combat Celebrant as attackers, choosing to exert Combat Celebrant as it attacks. Grub and Combat Celebrant trigger.
Resolve the Grub trigger, putting a -1/-1 counter on Combat Celebrant and then creating a tapped and attacking token copy of it.
Combat Celebrant dies as a state-based action due to having 0 toughness.
Resolve the Combat Celebrant trigger, causing you to untap all other creatures you control and causing you to get an additional combat phase after this one.
Repeat each combat phase, using the Combat Celebrant token instead.

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.