So, went through the quest for Maridia to get Dawnstar, and all that jazz. Completed the quest, got teleported to the air to talk to her, she sent me back to the ground. But, my companion did not come with me, and now she is stuck in the kilkreath catacombs behind a door that is now locked and requires a key. I cannot get a new companion because she is still alive and technically still following me, but she can't get out and I can't get in. She will not follow no matter how many times I fast travel, and I can't find a key to that door. If anyone knows where to get a key, or how to get her unstuck I would be very appreciative.

I'm in the same boat, I even loaded an earlier save, and after fighting that battle another ten times to win again, I discovered that even trying before I grab the sword, there is still no way to get them out of there. Hey Bethesda, why can't the stupid door unlock after you kill Malkoren?

wow, same thing for me. after chalking it up as a loss and shedding a few dragonborn tears, i went to try and get myself a new companion. no deal...please Bethesda, help me get my lydia out...its cold and lonely in there!! (shes also carrying a few things for me, but i care more for her safety)

Where's the key?

weird....so i went back to my house in Whiterun and LYDIA was sitting at the corner table in my bedroom...chilling. she wasn't wearing the helmet i gave her and thought maybe she didn't have my loot. opened her inventory and everything was there. i had to ask her to follow me again...she somehow found a way to escape.

Same thing happened to me and i used the Shout that detects life to confirm that they are indeed stuck in there. This should be a quick fix bethesda so just make that door open already!!!!!!!!!!!!!!!!! Praying for the patch...