The battle is very similar with the one held with the Lesser Shade. It can't be harmed by any physical weapon, so you must use Mirania's nature magic to make him vulnerable or to infuse your weapons during the fight. As with the Lesser Shade, it will disappear after he's taken some damage, often taking control of one of your allies and leaving some skeletons to fight. To break the control over your allies you can difuse any healing magic circle or you can defeat your allie and revive him.
After the fight you'll be awarded with the Paladin.
Element: Darkness (weak against Light)