Ratadrabik of Urborg + Leyline of Singularity + Ticking Gnomes

How it works

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Activate Ticking Gnomes by sacrificing it.
When Ticking Gnomes dies, Ratadrabik triggers, creating a token copy of Ticking Gnomes that is a 2/2 legendary Zombie in addition to its other types.
Resolve the Ticking Gnomes ability.
Repeat using the Ticking Gnomes token

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

1–2 · Exhibition & Core

Spellbook classifies this as Spicy — not for these brackets.

3 · Upgraded

Allowed in this bracket.

4–5 · Optimized & cEDH

All combos are allowed.