Responses
It's also due to the hair ornament that Jeanette gave to Athy.. That dark Claude (forgot his name) was the one who suggested Jeanette to give it as a gift.. He most probably cast a spell on it, so that when Athy came in contact with Blackie the spell got activated and caused her powers to go out of control.. ╮( ̄▽ ̄)╭
I'm not sure whenever what I'm thinking is right or wrong, but do you remember what happened when Athanasia's mana went nuts? That time when she absorbed Blackie and Claude lost his memories? She was playing with Blackie at the picnic and then encouraged Jennette to touch him. When Jennette started petting Blackie, Athanasia was only looking. But when she touched Blackie again - and all this craziness happened. That means it's due to Jennette's magic that everything that came next happened - she made Athanasia magic went nuts, which lead to Claude memory loss. Athanasia once said that this world exists solely for Jennette and it's scary when you think how right she was...