Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight + Blessed Sanctuary + Aquastrand Spider

How it works

Kill Aquastrand Spider.
When Aquastrand Spider dies, its persist ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it due to its graft ability.
When Aquastrand Spider enters, Blessed Sanctuary triggers, creating a creature token.
When the creature token enters, Aquastrand Spider triggers, moving a +1/+1 counter from it to the creature token. Aquastrand Spider dies as a state-based action due to having 0 toughness.
Repeat from step 2.

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.