Timestream Navigator + Recruiter of the Guard + Soulherder

Decks

How it works

Activate Timestream Navigator by paying , tapping it and putting it from the battlefield onto the bottom of your library, causing you to take an extra turn after this one.
Blink Recruiter of the Guard using Soulherder.
When Recruiter of the Guard enters, it triggers, searching your library for Timestream Navigator and putting it into your hand.
Cast Timestream Navigator by paying .
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.