mrhiddles:

But is that even legal to publish?

I mean, the best example I have at it being legal in any way, shape or form is Loki by Mike Vasich.

Advice?

My answer is assuming that you live in the USA or in a country whose copyright laws are similar:

Mythical characters and stories are not copyrighted, however, some translations are. So basically, if you want to copy and sell a translated work and don’t get the permission of the translator and publisher, that is illegal. BUT if you want to write your own text and sell it that is 100% legal.

There are 1000s of works based off mythology, and no one is legally able to hold a copyright on a historical or mythical story/character/icon such as Ymir. However, you are allowed to hold a copyright on your particular interpretation and presentation of a character. For instance, it wouldn’t be legal to write and sell a novel about the Thor from Marvel Comics. So if you wanted to write a comic book about Thor, thats totally fine, but you have to make sure you design the character to look different than the Marvel Thor, and that you don’t copy any background story that was unique to Marvel’s telling of the story.

I hope that helps answer your question and you go ahead and write your story!