Ultimecia, Time Sorceress // Ultimecia, Omnipotent + Moonmist + Isochron Scepter + Y'shtola Rhul

Decks

How it works

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Activate Isochron Scepter by paying and tapping it, casting a copy of Moonmist without paying its mana cost.
Resolve Moonmist, 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, Y'shtola Rhul triggers, blinking Ultimecia, Omnipotent and causing it to re-enter the battlefield as Ultimecia, Time Sorceress.
Whenever Ultimecia, Time Sorceress enters the battlefield, 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.