Shock Mountain will have few NPCs.
Shock Mountain used to be at peace where 10 dragons lived and guarded it, however five wandered off, eventually to the crux system, then 2 more wandered off, possibly to the castle world leaving the 3. They were partially corrupted when a small maelstrom probe used Cyberplexus to find the mountain, then created a massive portal to it.
Two succumbed to the corruption, but one was able to retain sanity and control, and pushed back the infection a bit. The other two, due to their power, were not controlled by the essence but went mad and were sealed by the sane one up in the floating island. The mountain is slowly digitalizing, and the Nexus Force has only a very small presence there. The player helps the last dragon, and finally goes to reclaim one of the treasures that the dragons used to guard that is hidden in the cave(s).
He then lets you go into the floating island, where you can fight the two dragons, it is also where the X boss battle will take place, and is where Imaelstroginations will appear, and they cannot leave.
Some gameplay ideas:
Random flashes of light, making it harder to see, rain, also obscuring vision, metamorphic enemies who change depending on the player's level, a boss battle where you fight two dragons, and a cave with lots of booby traps to get an ancient artifact.