Incredible, looks amazing!
To the wish list!

Edit. - DEMO GAMEPLAY

So the written description said battling mythical creature but the trailer show that it's more about exploration video game with no violence at all. So which is it?

Looks interesting although the player seems to have problems with the controls.

I expected more of a focus on dental hygiene, just from the title.

Looks interesting.
However I have doubts that the game will have audio in 9 languages.

Looks really interesting! The art style reminds me of Death's Door and Black Book and the idea of playing an old man with a semi-independent magic staff sounds really unusual. I hope they do some interesting stuff with that.

I'm also very keen on seeing more games inspired by mythologies we don't see that often in games. Just out of curiosity, though (forgive my ignorance): Is there some sort of historical connection between Icelandic and Russian myths? I lol'ed

Published now by Merge Games, which abandoned GOG some time ago. Unfortunately, it will probably be removed from GOG's "Coming Soon" games.

We'll know on or around the 12th of September, if that's the case.

Game's been out on Steam for months, and it's not the only one with an empty store page on GOG - WTF is going on?

What do you mean empty store page? Seems to have the details filled for me.

Empty in this case may be in reference to the first clause and just an unusual choice of word, that it's been released on Steam since early September and is still unavailable for purchase on GOG. The adverts are all in place, the release has occurred, but still the shelves are bare.

*Also, it seems that Polecat1 guessed correctly, Steam now lists the language options as interface and subtitles only, rather than the full audio that was intended earlier in development.

Sure, everything but the game. Selfloss, The Axis Unseen, The Plucky Squire, Flowstone Saga, all games that have been out for weeks and months but aren't on GOG. No explanation, no release date, nothing.