Kiliko Lagen  

Nathanael, キリコ=ラーゲン

Hector's assassination was supported by Lagen, who played a significant role in it. As an antagonist, he seeks power over Sana through manipulation. It was Lagen who pushed Belca off the cliff. He experiments on the Amontel and is the son of one of the Elders. While not much information about his past or motivations is available, it's clear that Lagen has a desire to vanquish the Elders.