The Arcane demon can be found in the 5th floor section C in the Slayerdungeon of Prifddinas. You need to have done the The Princess and the Warrior quest to access this area. As with all demons, the creature is weak to Darklight and Silverlight attacks. The Arcane demon is also extremely weak to light spells, such that playes hit 50% more often than they usually would. They have a very high defence for ranged and melee attacks, so maging them is advised. They have two attack styles, Melee and Magic. Their magic attack does much more damage than their melee attack, but the melee attack is very accurate.