Hi, basically all the lenses cited above by you and felixkh are ultra wide angle (low focal length in mm) so I can only assume they'll work well with photographing the sky. I have no particular knowledge about northern lights though. Have you also considered a fish-eye lens such as the Pentax 10-17mm? That might be fun.
In any case I'm guessing you won't have a lot of available light so you probably will shoot wide open (at wide apertures ie low f/ numbers). In this regard all of the cited lenses are more or less equivalent. Most of them are zoom which means you'll get flexibility (for instance 12-24mm, 12 is ultra-wide while 24 is just slightly wide - you can check the result by setting your 18-135 at 24mm). With the 15 limited (I love this lens) you lose all that flexibility but you gain size/weight and luxury build? Great IQ too but that is also true of the Pentax 12-24 at least. Your call what is most important to you!
In short: I don't think there is a right or wrong answer to your question. And regarding other uses: of course there are. They just depend on your imagination. One particular thread in this forum comes to mind for inspiration:
https://www.pentaxforums.com/forums/lens-clubs/86234-15mm-limited-controls-my-mind-club.html
Have fun!