Short answer
The useful part first.
Gloom and The Citadel are a paired set of biome variants. On a Final Ascent map, Gloom replaces Caldera and The Citadel replaces The Kiln. They appeared exclusively for the first two weeks after release; afterward, the daily map randomly chooses the Caldera/Kiln pair or the Gloom/Citadel pair.
What appears in a run?
Original pair
Caldera → The Kiln
The established fourth-biome sequence remains in the rotation.
Final Ascent pair
Gloom → The Citadel
The new variants occupy the same two stages when selected.
Why did every map show the new pair?
The developers forced Gloom and The Citadel into the map pool for two weeks after the August 11 release so players could reach the new content. That launch rule is temporary. It does not mean the original Caldera and Kiln were deleted.
What changes after the launch period?
PEAK returns to a random variant rule within its daily map. One day may use Caldera and The Kiln; another may use Gloom and The Citadel. Because the island changes every 24 hours, restarting the same day’s map does not guarantee a different biome pair.
Is this a Gloom route guide?
No. This page answers the rotation question using official evidence. Gloom hazards and Citadel routes are visual, map-dependent tasks. We will not publish precise survival steps or locations until they can be repeated in-game and supported with screenshots that actually prove the route.