Varga

Varga was a demon, once part of the followers of the Demon Lord. Long before the story starts, the Demon Lord threatened to conquer the world, but Luna's ancestor Duke Leghion merged with Varga and struck down the Demon Lord. After the battle Duke Leghion sealed himself together with Varga under the caslte.
Once the castle is under attack in the beginning of the story, Varga merges with Luna to help her with her pure will to defend Rimzbel.