Medomai the Ageless + Capsize + Kenrith's Transformation

How it works

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Deal combat damage using Medomai, triggering its ability, causing you to take an extra turn after this one.
Move to your next turn.
Cast Kenrith's Transformation by paying its mana cost, attaching it to Medomai and causing it to lose its abilities.
When Kenrith's Transformation enters, it triggers, causing you to draw a card.
Declare Medomai as an attacker.
Holding priority, cast Capsize with buyback by paying , returning Kenrith's Transformation and Capsize to your hand.
Repeat from step 1.

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.