Locked Door in the Hatchery
There’s a purple icon beyond it.
For anyone who is stuck on it. You gotta shoot the tank next to the broken cables from the room above.
Which you get to from the floor in the nearby side room.
This set of screenshots should help:
Update: It seems that locked doors like these are randomly generated because my Hatchery didn’t have this door. I did come across it but in another Dungeon named The Dark Conduit, whereas the guy above me seems to be in the Putrid Domain.