User blog comment:B214/Question and Answers 6/@comment-9595671-20160714212150/@comment-24.113.252.213-20160715010806

Odin is the Chief God of Norse Mythology. So of course the Valkyries serve him primarily. Freyja is simply their Boss/Supervisor.

Maybe the Valkyries are former humans like the Einherjar, but were called upon by the Norse Gods for their high magic potential, instead of their battle prowess. So a Valkyrie is a Female who has high magic potential, trianed to become a powerful magician, and Freyja turned them into Valkyries. Similar to how Sun Wukong was turned into a Buddha for his service.