It is a universe where life after death is a guaranteed choice. The soul ventures on to the other side of the vail, where it is adopted into a realm. These realms are based on the religions the mortals create. These energetic beings shaped, combined and possibly influenced themselves to take the role that the humans wanted. Energy from the other side can be connected with, leading to contact. Who knows what adventures can happen with an opportunity like that?
All books with the "Hel's Hoard" sticker belong to Hel, the Goddess of Helheim, ruler of the underworld in the Nordic realm. She is a dragon that is very protective of things in her hoard. Keep that in mind.