How to seal the night? Are you asking as a human? Or as a demon?
Christophorus (ミストラル) is a supporting character and optional boss in Nights of Azure, and a returning character in Nights of Azure 2. She is a masked pure-blood demon who frequently haunted the Ruswal Opera House until meeting Arnice. Her split personality and mysterious motives make her difficult to understand, but she has developed a soft spot for Arnice over the years.