[SixOfSpades]

The true Point of No Return comes later. There's a hallway with 4 doors all leading in one direction--to beat the level, you have to clear out each of those 4 rooms. After that, the only way out is further down.

The level that you're on (the one with the different-colored wardstones) is also very important: The doors you open here tend to close themselves--and never open again, not even for the wardstones--after a couple of hours, or so I've heard. People say that they've cleared this level, gone back upstairs to stash their stuff and Rest, and then they've come back downstairs to find the way barred to them.