Ultimecia, Time Sorceress // Ultimecia, Omnipotent + Tetzin, Gnome Champion // The Golden-Gear Colossus + Encroaching Mycosynth + The Mind Stone

Decks

How it works

Declare The Golden-Gear Colossus as an attacker. It triggers, creating two 1/1 Gnome artifact creature tokens and transforming Ultimecia, Time Sorceress into Ultimecia, Omnipotent.
Ultimecia, Omnipotent triggers, causing you to take an extra turn after this one.
At the beginning of your end step, The Mind Stone triggers, blinking Ultimecia, Omnipotent. It'll enter the battlefield as Ultimecia, Time Sorceress.
When Ultimecia, Time Sorceress enters, it triggers, causing you to surveil 2.
Repeat each turn.

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

1–2 · Exhibition & Core

Spellbook classifies this as Ruthless — not for these brackets.

3 · Upgraded

Spellbook classifies this as Ruthless — not for these brackets.

4–5 · Optimized & cEDH

All combos are allowed.