This is the anthology of a fantasy saga, which is assigned to the nordic/germanic mythology. Old sagas and legends, long forgotten gods, warriors, giants, Einherjer, fallen heroes and a country shattered by war. Many scenes take place in the north of the country, which means that snow and ice are often depicted. It would therefore be good if this detail could be integrated into the cover.
A possible representation could be a descending weapon in which a battle scene is depicted. Giants, Einherjer, gods etc. Anything possible. Another possibility would be the view of a hero (red coat, hammer, grey hair) over a scenario. You can also orient " a little bit" yourself on the covers of the single volumes, if you don't have ideas.
The cover should also appear at a distance in the ebooks shops, e.g. on Amazon, and not only zoomed in closer. It is also important that the title and author are clearly recognizable from a distance. As this is a bestselling saga, the cover has to be convincing. ;)
Important note: Take a look at the fantasy-covers on amazon.de (i.e. in German-speaking countries). A cover that works on amazon.com doesn't have to work in German-speaking countries. And dont forget that it's "heroic fantasy". It was supposed to give the impression of an adventure. I have attached some examples to designs that I like. It doesn't have to be, it's just a few styles.
There are no limits to your creativity, the main thing is to stay with the topic (see description) and knock me out!