Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight + Phyrexian Altar + Propeller Pioneer + Effects that Alter a Creature's Power/Toughness (Anthem Effects)

Decks

AnyEffects that Alter a Creature's Power/Toughness (Anthem Effects)

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How it works

Activate Phyrexian Altar by sacrificing Propeller Pioneer.
When Propeller Pioneer dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
When Propeller Pioneer enters, its fabricate ability triggers, putting a +1/+1 counter on it.
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.