Abby, Merciless Soldier + Ashnod's Altar + Mirror of Life Trapping + Chromatic Orrery

How it works

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Cast Abby from the command zone by paying plus commander tax if applicable.
Abby triggers, creating a number of 1/1 Fungus Zombie creature tokens named Cordyceps Infected equal to the amount of mana spent to cast it.
When Abby enters under an opponent's control, Mirror of Life Trapping triggers, exiling Abby.
Choose to return Abby from exile to the command zone.
Activate Ashnod's Altar by sacrificing a Cordyceps Infected token, adding .
Repeat step 5 until you have enough mana to cast Abby.
Repeat from step 1.

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.