Jan Jansen, Chaos Crafter + Haunted One + Retribution of the Ancients + Goblin Bombardment + Artifact Creature that is a Gnome and/or Artificer

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How it works

Jan Jansen and the additional Gnome or Artificer do not have a +1/+1 counter on them.
You control at least one additional artifact creature.
Artifact Creature that is a Gnome and/or Artificer

Activate Jan Jansen's first ability by tapping it and sacrificing another artifact creature you control except the Gnome or Artificer.
Jan Jansen triggers, causing it and creatures you control that share a creature type with it to get +2/+0 and undying until end of turn.
Resolve the Jan Jansen ability, creating two Treasure tokens.
Activate Goblin Bombardment by sacrificing Jan Jansen.
When Jan Jansen dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
Resolve the Goblin Bombardment ability, dealing 1 damage to any target.
Activate Jan Jansen's first ability by tapping it and sacrificing the Gnome or Artificer.
When the Gnome or Artificer dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
Resolve the Jan Jansen ability, creating two Treasure tokens.
Activate a Treasure by tapping and sacrificing it, adding .
Activate Retribution of the Ancients by paying and removing the +1/+1 counter from Jan Jansen and the other Gnome or Artificer, giving a creature -2/-2 until end of turn.
Repeat from step 4.

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

1–2 · Exhibition & Core

Allowed in this bracket.

3 · Upgraded

Allowed in this bracket.

4–5 · Optimized & cEDH

All combos are allowed.