Molderhulk + Cloudstone Curio + Dual Nature + Borborygmos Enraged

Exhibition

How it works

You control at least one Swamp and at least one Forest that enter the battlefield untapped.
You have at least seven creature cards in your graveyard.
You have at least one Swamp card and at least one Forest card that enter the battlefield untapped in your graveyard.

Activate a Swamp and Forest by tapping them, adding .
Cast Molderhulk by paying .
When Molderhulk enters the battlefield, it, Dual Nature's first ability and Cloudstone Curio trigger.
Resolve the Cloudstone Curio trigger, choosing to return nothing to your hand.
Resolve the Dual Nature trigger, creating a token copy of Molderhulk.
When the Molderhulk token enters the battlefield, it and Cloudstone Curio trigger.
Resolve the Cloudstone Curio trigger, returning the nontoken Molderhulk from the battlefield to your hand.
When the nontoken Molderhulk leaves the battlefield, Dual Nature's second ability triggers, exiling the token Molderhulk.
Resolve the token Molderhulk's trigger from step 6, returning a Swamp from your graveyard to the battlefield.
When the Swamp enters the battlefield, Cloudstone Curio triggers, returning another Swamp from the battlefield to your hand.
Resolve the nontoken Molderhulk's trigger from step 4, returning a Forest from your graveyard to the battlefield.
When the Forest enters the battlefield, Cloudstone Curio triggers, returning another Forest from the battlefield to your hand.
Activate Borborygmos Enraged twice by discarding the Swamp and Forest, dealing 6 damage to any target.
Repeat.

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.

How it works

You control at least one Swamp and at least one Forest that enter the battlefield untapped.
You have at least seven creature cards in your graveyard.
You have at least one Swamp card and at least one Forest card that enter the battlefield untapped in your graveyard.

Activate a Swamp and Forest by tapping them, adding .
Cast Molderhulk by paying .
When Molderhulk enters the battlefield, it, Dual Nature's first ability and Cloudstone Curio trigger.
Resolve the Cloudstone Curio trigger, choosing to return nothing to your hand.
Resolve the Dual Nature trigger, creating a token copy of Molderhulk.
When the Molderhulk token enters the battlefield, it and Cloudstone Curio trigger.
Resolve the Cloudstone Curio trigger, returning the nontoken Molderhulk from the battlefield to your hand.
When the nontoken Molderhulk leaves the battlefield, Dual Nature's second ability triggers, exiling the token Molderhulk.
Resolve the token Molderhulk's trigger from step 6, returning a Swamp from your graveyard to the battlefield.
When the Swamp enters the battlefield, Cloudstone Curio triggers, returning another Swamp from the battlefield to your hand.
Resolve the nontoken Molderhulk's trigger from step 4, returning a Forest from your graveyard to the battlefield.
When the Forest enters the battlefield, Cloudstone Curio triggers, returning another Forest from the battlefield to your hand.
Activate Borborygmos Enraged twice by discarding the Swamp and Forest, dealing 6 damage to any target.
Repeat.