Vápnthjófr saga

Rotaimo was the name for a sami death realm, ruled by Ruohtta, the god of disease, where people who didn't live according to the natural order ended up after death. This might be a later addition to the religion, however, influenced by the christian idea of hell (Cause the sami is one of many indigenous groups to be forced to convert to christianity...)

Freyr was told to have a self-swinging sword. He lost it in Jotunheim while courting a jotun woman, though.

During the Viking age, Freyr's sacred places were supposed to be free of violence. Fighting there were forbidden and you couldn't bring weapons either. (There were still sacrifices made for him, though, but in this setting animal sacrifice is of course not a thing)

The east coast she refers to is the so-called "High coast", a part of the Baltic coast of northern Sweden. It really is a lovely place, with steep cliffs and rocky forests. (Tip: If you visit sweden, go hiking in the Skuleskogen national park!)

To translate some of the viking names for countries: Gårdarike is western Russia, Bretland is Britain and Särkland is the middle east. (Shirin probably personally calls it Persia, but she used the Särkland name here so the others will know what she refers to. And yes, there are pine martens in Iran)

Freyr's island = Frösön. That island was named after Freyr. Lake storsjön also has a lake named after Njord.

In sami mythology, the world was believed to be made up of several different realms, (The mortal, the divine and the dead) and the schamans traveled between the realms as a means to communicate with gods or the dead. He was led by guardian spirits in the visits to those other realms.

Noaidis were sami schamans. The sami schaman drums were covered in symbols, and was used in rituals. The schaman would use it to read signs from the future or from other realms, or to get into a trance where their spirits could leave their bodies and travel between realms.

Stallo was a being in Sami folklore. He was a man-eating giant who wasn't vey bright, and stories of him are often about him being defeated by being outsmarted.