After searching with google translator on the Polish forum, walkthrough and walking to and fro in the underground and the temple I still cannot find the gatekeeper who should have the teleport gate back to the mine next to him.
It's quite embarassing as it looks like I'm the only one who isn't able to locate him.

I'm sure he is somewhere around, but can you please tell me exactly where?
I've chosen the Beliar path (ah well, unintentionally, but now I'll stick with it) and I would love to go to the upper world after killing every demons and abnormal creatures that move.