Based on available information, there is no character named "Ertzen" in the anime "Übel Blatt". The search results refer to a character named "Eltzen", which may be a variant of the name the user is looking for.

Eltzen is a companion who joins Elseria Rahnclave on her adventures. He is characterized as an elegant young man who wears glasses and serves as the strategic brain of the group. Demonstrating a pronounced talent for manipulating magical formulas, he wields his skills in magic adeptly to support the party. Eltzen holds a strong curiosity regarding the power and existence of fairies, which sometimes causes him to act rashly when encountering related phenomena. His manner of addressing Elseria as my lady gives him the air of a knight dedicated to protecting her. Originally in the service of the Rahnclave household, he has clear memories of Elserias growth and the events of her past. His extensive knowledge and experience provide great support for the group, adding depth to the story through his presence. No reliable direct information exists regarding his personal motivations, his specific role in the plot, the full scope of his notable abilities, his character development, or his key relationships with other characters beyond Elseria.