|“||Oh, I am but a wizard, a guardian of man and beast; and indeed I am both.||”|
Arhu is a wizard in Cyseal who called for Source Hunter's help for investigation of the murder of Councillor Jake.
You first meet Arhu when you try to enter Cyseal after the fight with Orcs on the beach. He recommends to go to Aureus the Legion commander and start investigating the crime. The very second floor of Legion Headquarters is Arhu's home. In the monetary he usually takes the form of a white cat. He sells fire and earth skillbooks, some potions, some gear, some resurrect scrolls and the Identifying Glass, Repair Hammer and Mortar and Pestle.
Cyseal is protected by magical ballistas Arhu made. Without them, the city would have already been flooded by the Undead and Orcs. But not only he succeeded in invention; there is a huge robot that suddenly went berserk. Arhu SparkMaster 5000, the insane robot, is the first boss you meet in the game. You can find details in this link.
Later on, he takes advantage of the ability to become a cat, and helps the Protagonists to infiltrate into the Immaculates' town; Silverglen and Hunter's Edge.
You can have a chance to fight him during the quest A Forge of Souls. According to Cassandra, he stole the Source Sapphires of the rarest kind. He is really strong.