Szilard Quates

A sadistic old man. Other immortals tend to view him in fear, and when they see him, they run. It's perfectly justified of course-

After Szilard developed the 'imperfect' immortal potion (where those who drink cannot be harmed but can age) he often fed it to others before 'eating' them. From doing that he has accumulated a lot of information without having to work for it. In the Light Novels Firo admits that all of the joy he has ever felt seems to pale in comparison to Szilard's joy in 'eating' others.

He created several homunculus, all of which eventually betrayed him until at last he created Ennis, giving her only fighting abilities, laws, and daily butler stuff- no ethics, no morals, and no religious views.

Trivia

 * His name, Szilard, correctly pronounced in Hungarian (his original country) is See-laurd.