Balen

Balen (ナスターシャ) was the teacher of Princess Keno Fasris Invern.

Background
Balen appears to serve as a teacher under the royal family of the Kingdom of Inveria.

The Vampire Princess of the Lost Country Arc
During breakfast, Annie Fasris Invern informed her husband that Balen would instruct Keno in her lessons after she finished her magic training.Overlord Bonus Volume Chapter 1: Encounter In The Lost Country

Abilities and Powers
It is unknown what subject that Balen excelled though it appears the the instructor was competent.

Annie Fasris Invern
Annie referred Balen as sensei indicating respect for the person.

Keno Fasris Invern
Balen was Keno's instructor.

Trivia

 * It is presumed that Balen suffered the same fate as the rest of the inhabitants of Inveria and was turned into a zombie.