Breath of Fury + Barbarian Class + Creature with Mobilize

Decks

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How it works

Declare the creature with Breath of Fury attached and the creature with mobilize as attackers, triggering the creature with mobilize, creating at least one 1/1 Warrior creature token that is tapped and attacking.
Deal combat damage using the creature that has Breath of Fury attached.
Breath of Fury triggers, causing you to sacrifice the creature it is attached to, then attach Breath of Fury to the Warrior token, then causing you to untap all creatures you control and to get an additional combat phase after this one.
Repeat each combat phase.

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.