This is just a theory.. since Athy has abundant amount of mana in her, Diana's body could not keep up with Athy's growth inside her tummy.. I remember Claude saying to Diana to let go of the baby since it was the main reason she was dying.. It could also be the main reason why Claude hated Athy before since Diana chose to keep her and died instead of living with Claude..
yeah. after being betrayed by both his brother and ex fiance, claude lived a life devoid of trust. until he met diana. but when diana got pregnant it threatened her life and claude was afraid of losing her. just like he lost his mom. we also have to keep in mind that claude doesnt know bat shit about having an emotional relationship so he didnt give af about some child inside his lover's body because he saw it as the reason diana was dying. so when athy was born, he abandoned her. but he couldnt kill her either cause he kept thinking of diana.
I’ve got a question!like Claude loved Athys mother but why did he hate athy at the beginning I mean she’s the child of the women Claude loved!