Nystrom was a man looking for riches with his partner Anders inside the Twilight Sepulcher. They pretended to be priests of Nocturnal to get to the valuables, which Anders said were found inside Pilgrim's Path.
While undercover in the Twilight Sepulcher he was assigned a mentor, Lythelus. Nystrom was prying about the obstacles in Pilgrim's Path and managed to coax information out of Lythelus, but it was in riddles. He planned to meet up with Anders to share what he learned so that they may attempt the obstacles. Anders instead killed him and left his body in the first room of the Twilight Sepulcher, where Nystrom's journal still rests.
Next to his remains is an enchanted leveled war axe.
If the Dragonborn asks Gallus Desidenius what they will face in the Pilgrim's Path, they will receive an optional objective to "Retrieve Nystrom's Journal" nearby.
- Nystrom and Anders are in reference to Swedish guitarist, Anders Nyström, who founded the metal band Katatonia. In Nystrom's Journal, the phrases Lythelus mentions are the names of a Katatonia album and track.