Updated for patch 9.19
Transforms to his Demon Form for 6 seconds. While in Demon Form, drains health from nearby enemies, dealing 40 / 80 / 120 magic damage and healing himself for 30 / 60 / 90 each 0.5 seconds for each enemy in range. At the end of the transformation, sends out a Soul Flare, dealing 300 / 600 / 900 magic damage to all nearby enemies. In total, for each enemy, the drain can deal 480 / 960 / 1440 magic damage and heal for 360 / 720 / 1080 health.
Demon's basic attacks have a 40% chance to reduce target's current mana by 20 and restore mana to the Demon.