Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight + Ashnod's Altar + Reputable Merchant

How it works

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Activate Ashnod's Altar by sacrificing Reputable Merchant.
When Reputable Merchant dies, its innate ability and persist ability trigger.
Resolve the Reputable Merchant trigger, putting a +1/+1 counter on a creature you control.
Resolve the persist trigger, returning Reputable Merchant from your graveyard to the battlefield with a -1/-1 counter on it.
When Reputable Merchant enters, it triggers, putting a +1/+1 counter on it.
Repeat.

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

1–2 · Exhibition & Core

Spellbook classifies this as Spicy — not for these brackets.

3 · Upgraded

Allowed in this bracket.

4–5 · Optimized & cEDH

All combos are allowed.