I finished watching season 3 of Ragnarok a few days ago and I've seen a lot of people being disappointed with the ending because they think it's "Magne was mentally ill and imagined everything, including the death of Isolde"... basically 'it was all a dream' plot (which I HATE).
Ragnarok
I don't think it's true because, during the graduation ceremony, I think Magne imagined Ragnarok. He kinda synced his imagination to the movements of the other Norse dieties, because he wasn't satisfied with his life as a normal teenager, without action and powers (which was stated in the fifth and sixth episode this season). The comics that he read gabe him the inspiration for it, and let him imagine that he was more then just an average boy for a few moments. After all, everyone around him got their happily ever after.
Talking To Signy
When he talked to Signy and held his shoulder and kneeled from pain because he imagined it very realistic, to the point where he almost thought it was happening. Or maybe he did it to "go back to reality".
Isolde
Later at the table with his friends he imagined Isolde with them, a way to say that he will never forget her and her impact on his life. Isolde fading strengthens this claim.
Other Scenes
In addition to this, throughout the series we saw scenes that can't be from Magne's pov, like scenes in the Jutul's house.
The Plot Twist
furthermore "it was all just in the hero's imagination" is a bad plot twist that everyone hates and until it's confirmed by the people who worked on the show I will not believe it. Also, why to put so much effort and make 3 season of a series just to say at the end "nahh jk it doesn't matter Magne is just mentally ill"??