Wish Seekers of the Storm had more loop variants so I tried my hand at it.

Config to make them and official variants happen pre-loop.
Or make them chance based on loops.
You can turn off individual variants if you dislike them.
You can configure things in game via Risk of Options.

The loop variants are meant to have enemy changes, this is currently part of LittleGameplayTweaks.
Viscious Falls and Disturbed Impact won't have Elder Lemurians or Void Reavers on stage 1.
Variants might still have some gamelplay differences. (Such as the slowing tar river on Aquaduct)

No idea how this mod interacts with Stage Aesthetics or Cooler Stages.

Weather changes in-game :

Inspirations :

• Titanic Plains : Version made for old trailers.
• Siphoned Forest : Aurora Borealis are cool, the one it already has was barley visible.
• Abandoned Aqueduct : Unused Tar River, Passage of time overfilling it.
• Wetland Aspect : Internal name FoggySwamp, Passage of time overfilling it.
• Aphelian Sanctuary : Eclipsing the Sun, ominous Lunar glow.
• Reformed Altar : Directly connected to Treeborn, so should be Golden Dieback on loop. More gold feeling.
• Scorched Acres : Unused Eclipse Weather. (they just tested it here for the menu for some reason)
• Sulfur Pools : Real Blue "Lava" Volcanos.
• Abyssal Depths : Red Plane color-scheme
• Sundered Grove : Spring/Autumn theme with Fruits
• Helminth Hatchery : Molten Gold

Basically all of these can fit the "Passage of Time" theme.
Even the more interesting changes such as Blue Lava Sulfur Pools, the background Volcano erupting as an idea for that.

Additionally this mod changes the Treeborn visible in Prime Meridian to Golden Dieback on loops.

Report bugs to @Wolfo.wolfo in the Risk of Rain 2 discord or RoR2 Modding discord.
If you're reporting a bug that isn't something obvious include the log file.

Not entirely happy with how some turned out but some are great.