This might be a stretch, but I'm hoping someone can help me with finding a German word I can't remember. A friend of mine (from Berlin) gave me a nickname years ago that I cannot for the life of me find. I think it was something like "Cloud King" or "Dream King" or something. It had to do with cloud castles or dreaming or kings or something. I was under the impression it was a pretty common thing from folk tales but I cannot find anything on the internet, despite my very best Google-fu.

Any help?

Thank you!

ETA: I'm 99% positive it was Marchenkonig, thank you to NapSauce and KillerMartinis! I feel so much better now.