Mordred

Mordred was the 9th seat of the Order of Diabolos and a knight in the round table. However, he was killed by Shadow and the Shadow Garden.

Personality
Mordred is a delusional-yet-foolish psychopath. According to Shadow, he is nothing more than a mook.

Return to Earth
It is revealed that, following his death, Mordred's severed head was transported to Earth alongside the Shadow and Beta. There, it was found by Akira Nishino, who experimented on it due to the vast amount of mana in his blood. He eventually attempted to inject Beta with his blood, believing that doing so would make her even stronger than the "First Knight". However, he was assassinated by Yuka before he could do so. Yuka would go on to instead inject Mordred's blood into Akane Nishino, causing her to go berserk until she was stopped by the Shadow. It is unknown what became of Mordred's head afterward, whether Beta took it back with her to the other world or left it behind.

Powers & Abilities
Mordred is slightly skilled swordsmen he use an artifact. However, he is nothing more than a weakling who stood no chance against Shadow and the Shadow Garden.

Trivia

 * Mordred is based on the knight Mordred from Arthurian legend.