Voltaic Construct + Time Vault + Karn, the Great Creator

Banned

How it works

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Activate Karn's +2 ability, turning Time Vault into a 1/1 creature until end of turn.
Activate Voltaic Construct for , untapping Time Vault.
Tap Time Vault to take an extra turn after this one.
Repeat for infinite turns.

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.