I really like the idea of a living dungeon or at least a malevolent intelligence inhabiting a place. I think it's a variation on stocking your dungeon with inhabitants that try to actively thwart the PCs.
Some questions that come to mind:
- how quickly can the dungeon make changes?
- what senses does the dungeon possess and is it possible to fool its senses?
- how many changes can the dungeon make in a given time-frame?
- does anything prevent the dungeon from creating/summoning extremely deadly traps/creatures/effects whenever it wants?
1- I was thinking that it might be limited to being unable to change the current floor, but can change a bit of it's layout over a long rest. It requires a longer time to fully change its layout.
2- sight (Darkvision) and hearing. No truesight, so you could be invisible and be fine. You might also be able to fool it with an illusion.
3- Unsure. Maybe something like 1 major change per hour? So, given an hour, it could place one trap that wasn't there before, or make a few slight changes to 2 traps.
4- It isn't
all-powerful, just really powerful within its space. It is limited to making things out of itself, so it could only make Constructs and traps. As for traps, it is limited by its creativity and time. The later floors might be traps that have sat the same for decades or centuries, as they have been reliable in keeping the adventurers out, or floors that have slowly evolved to include traps to kill every adventurer who has entered in the past several centuries.
I have been thinking about the story of the dungeon, and think it might be either a Prison for something, or a security system.
Prison: Much like the Minotaur in its labyrinth, something lies at the center of the Dungeon, something old and deadly. The dungeon uses the powers of the many adventurers as examples of things it has to protect against, in case the Prisoner gained such a power.
Security: Mighty wizard or secret society sits at the center of the dungeon, well known because their name is on the front door of the dungeon. They use the dungeon for two reasons.
1)Keep unimportant people away from them, because they don't want to be troubled by the locals who need a solution for their problems.
2) Test new initiates, who are trained away from the dungeon, and brought to it to reach the center.