Caspar Blankenheim is a marquis who marriedMargarita Blankenheim in order to obtain her dowry. After that, Caspar began to cheat on her with other women. He is the first person to be given her "gift", under the guise of it being a sleep medicine to help relieve him of stress.
Featured in...
Gift from the Princess who Brought Sleep (EC 609)
In Gift from the Princess who Brought Sleep, the first portion of the song is directed at him, discussing his relationship with Margarita; in spite of his lack of concern for her, Margarita still loves him. Caspar is the first person to receive the "gift", and during an instrumental, it's revealed that he's passed away as a result.
Connections to Other Characters
Margarita Blankenheim: Although Caspar made some sort of childhood promise to her, he had forgotten it by the time they became adults. Their marriage was born from politics, and it's clear that he only wanted her wealth. Soon, Margarita administers the "gift" to him, and he dies some time after that.