Lersatio

Lersatio was once a normal person and a citizen of Carlin. He, his brothers Arthei, Marziel, and Boreth, and Arthei's wife Kala, travelled to Yalahar in order to find a new home. From that moment on Marziel started keeping a diary.
Lersatio is a vain vampire who dreams to see his face in a mirror again, which is why he awakens when you break the mirrors near him. He is the second boss you will encounter during the Blood Brothers Quest. He spawns with 2 Vampires.
You will receive The Dust of Lersatio when you use a Blessed Wooden Stake on his dead body.

He fights till death. Uses Invisibility very often.

Knights: the best option is to Exori or Exori Gran as much as possible while keeping an eye on your health. That way you kill all the summons as well so they don't do extra damage.