During the creation process I have started to form a history for Kaduria. It's loose and I don't know the exact details myself, but I'd like to tell something about it.
As everyone knows Kaduria was constructed by dwarves, like Moria too. But that's only half true. In fact there was an older dungeon built by ancients. (You got to have ancients, because they are cool.) From this process there are still places and items left that are clearly something different than what dwarves made later. Then, who were the ancients? Were they elves or maybe dwarves that were more advanced in metal handling? Or could they have been humans? I like to keep that an open question.
There were also two other ancients. First of them is well known and there are still people left from the tribe that once inhabitated a part of Kaduria. Then there were also a third kind of ancients, who possibly were the oldest of them all. They were the ones who built the twilight gate.
So there is lots of ancient crap to be discovered. Powerful weapons and treasures. Dwarves were not interested in searching the dungeon when they took over. For them Kaduria was a place of mining operations. They couldn't care less about the ancients or the junk that was hidden somewhere. But dwarves were concerned about the twilight gate and it was hidden by them.