Cass, Hand of Vengeance + Griffin Guide + Phyrexian Altar

Decks

How it works

Griffin Guide attached to another creature you control.
You control an additional creature beyond those included above and the one that has Griffin Guide attached.

Activate Phyrexian Altar by sacrificing the creature with Griffin Guide attached.
When the creature dies, Cass and Griffin Guide trigger.
Resolve the Griffin Guide trigger, creating a 2/2 Griffin creature token.
Resolve the Cass trigger, returning Griffin Guide from your graveyard to the battlefield attached to another creature you control.
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.