Edit: Found it - "A Dark and Dangerous Place" by K_R_Allen. Deleted. Hey, guys! I remember reading fiction (probably on Royal Road) about dungeon, but can't find it now. What I remember: dungeon was in some kind of swamp monsters called it 'Mother' it created whole new race (?) at the beginning, there was party of adventurers sent to check dungeon and they decided to destroy it. Spoiler At the end of first volume it was almost destroyed, and at the beginning of second it moved to sewers of some city. When I last read it, author started second book/volume.
https://www.royalroad.com/fiction/2196/lair This one is close enough. But it didn't go to sewer. Maybe you mean welcime to man-eating dungeon? But it didn't called as mother
https://www.royalroad.com/fiction/11555/the-pale-dungeon-dropped This? Recently officialy dropped after long hiatus.
Found it! Kind of... "A Dark and Dangerous Place" by K_R_Allen. Apparently author got a lot of hate and troll comments and deleted it. Shame, it was a really good read
https://www.royalroad.com/fiction/19438/a-dark-and-dangerous-place?review=284579 It's no longer avaible, the author took it down from RRl Edit: I'm sure the novel was this one, it talked about a dungeon who called itself Mother and spoke in broken English, it started out as a swamp, and it said all the time "In muddy waters all are prey"
Yup can confirm sad to see that i was deleted, though I dropped it after it was destroyed and relocated it was still a good story.