It is known that his father, a former member of his village, forbade his son from joining the learning the ways of the force, as he did not wish for his son to live the life of an dark jedi. However, izzaldin joined in spite of his father's wishes in order to provide his wife and son with a comfortable life.
Now izzaldin is a dark jedi inexorably seeking vengeance against those responsible for the destruction of his village and the death of his own family. Despite his malevolent appearance, he is not inherently evil. He joins the forces of evil when promised a means of resurrecting his clan on mustafar or the chance to inflict his wrath against those who butchered them.
He undertakes actions that benefit the galaxy, albeit in his own gruesome and vigilante manner.
Izzaldin appears human when masked, though this is merely an illusion. Only his skull remains when his true form.