Casting Chaos Bolt, Rain of Fire, or Shadowburn grants Diabolic Ritual for 20 sec. If Diabolic Ritual is already active, its duration is reduced by 1 sec instead. When Diabolic Ritual expires you gain Demonic Art, causing your next Chaos Bolt, Rain of Fire, or Shadowburn to summon an Overlord, Mother of Chaos, or Pit Lord that unleashes a devastating attack against your enemies.