Arni Metalbrow + Thousand-Faced Shadow + Cloudstone Curio + Dockside Extortionist

Banned

How it works

Declare Dockside Extortionist as an attacker.
Arni Metalbrow triggers, causing you to pay to put Thousand-Faced Shadow from your hand onto the battlefield tapped and attacking.
When Thousand-Faced Shadow enters the battlefield, it, Arni Metalbrow and Cloudstone Curio trigger.
Resolve the Cloudstone Curio trigger, choosing to return nothing to your hand from the battlefield.
Resolve the Arni Metalbrow trigger, choosing not to pay.
Resolve the Thousand-Faced Shadow trigger, creating a token copy of Dockside Extortionist that enters the battlefield tapped and attacking.
When the Dockside Extortionist token enters the battlefield, it, Arni Metalbrow and Cloudstone Curio trigger.
Resolve the Dockside Extortionist trigger, creating at least two Treasure tokens.
Activate two Treasures by tapping and sacrificing them, adding .
Resolve the Cloudstone Curio trigger, returning Thousand-Faced Shadow to your hand from the battlefield.
Resolve the Arni Metalbrow trigger, causing you to pay to put Thousand-Faced Shadow from your hand onto the battlefield tapped and attacking.
Repeat from step 3.

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

1–2 · Exhibition & Core

Spellbook classifies this as Banned — not for these brackets.

3 · Upgraded

Spellbook classifies this as Banned — not for these brackets.

4–5 · Optimized & cEDH

Spellbook classifies this as Banned — not for these brackets.