Vápnthjófr saga

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.

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.

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.

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

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)