So, probably I will make another remodeling of the campaign (here you can find more info about it) and this time changes will be even bigger than during previous reboot. However, I'll not resign from the idea of the surface world, most likely I will separate both ideas - another maps, background and rules for the Ortix world, another for twisted and bizarre (truly weird?) Underworld Kingdom. Are they connected to each other? It will depend only on GM's decision :-)
Here is a list of things that potentially will appear in the "new" Underworld Kingdom:
- Jungle Caves (I don't see any reason to drop this idea);
- Red Moon Caverns as some connection between one of the moons and kingdom of Underworld? Why not? :D
- Megastructure - artificial level, inhabited by savage tribes and deranged living machinery. Heavily inspired by works of Tsutomu Nihei, it bears some resemblance to Gigacrawler;
- Black Sea and the City of Serpents (not necessarily inhabited by Ho-ru);
- Green Light Caves (haunted and dangerous place of madness and illusion);
- Land of the Dead (inhabited by the Dead Ones);
- Lava Caves;
- Mutation chambers (or maybe - mutilation chambers? :D);
- Palace of the Black Emperor (bizarre and slightly surreal sub-dimension - more info soon!);
- Icy Caves;
- Darkforge (another industrial level);
- Frog River;
- Great Fungal Forest;
- Watcher's Pit;
- Crystal Caves;
- Death Pits.
- Blackcrag Fortress ("mountain inside a mountain" - I'll try to explain it in the future);
- Tesseract Chambers;
- Ancient graveyards...
- ...and probably many more.
I know that these are only names, but they can give you some ideas on how it will look like. In addition I'll try to expand this list in the future and add links to the articles about specific items.
Another idea that came to my mind is that these locations will not connected in the "only right" way - more likely I will include general guidelines about connections between different layers (and some additional rules about moving between larger parts of the Underworld) and every DM will be able to connect different parts of the Underworld Kingdom in his own way.