Board Thread:Lore Discussion/@comment-6150460-20130202092040/@comment-5558140-20130211014715

the dark brotherhood i believe define him as "everything and nothing". they consider sithis to litterally be the "void". if one were to take that into context, you could say that sithis is everywhere and in everything at all times. he is less a characterized deity and more of an element. if the aedra and daedra could be considered the catalyst for the creation of nirn, then you could consider sithis the "clean slate" upon which it occured.