Eucliwood Hellscythe

Eucliwood, also called Eu or Yuu for short, is a necromancer who brought Ayumu back to life to be her guardian and has been living with him since. She wears an armor that suppresses her abilities and doesn't talk because her power can make every word spoken become reality. Instead, she communicates to others by using note pad, which usually pertains to her appetite. Although seemingly emotionless and mute, it is shown that she cares deeply about her friends and other people, even Ayumu though she considers him to be her servant. She does not like the word "death" taken lightly especially since her powers can instantly take a person's life. Ayumu often daydreams about her speaking in a cutesy manner.

She resurrected The King of the Night as a zombie, but eventually killed him before the start of the series.
It is revealed that when she was younger, she was able to speak without the consequences of magic.