For example, adom had these greater molochs. Very slow heavy armored hard hitting monsters. Normally (without armor penetrating arrows of demon slaying) you would not try to attack these.
The question is: Is there such a think in tome?
Are there monsters you should just run away from?
Maybe we need some,
or should you be able to kill everything?
What do you guys think?
That brings me to the "moving wall" idea.
A monster that does not hit you, but moves towards you and has~10k hp with high resists. The only way to get out is to dig/teleport away when he gets you stuck. Obviously, there should never be more than two on a level (3 can get you stuck in a corner for ever).
Now imagine a level filled with moving walls with corridors on a grid pattern (like the roads in new york city). They 'patrol' like the sand worm tunnelers and they are neutral. If you attack one they become hostile and move towards you