Anders is a fun-loving mage, jokester, and cat lover. He has a strong belief against the mages being kept captive in the Circle of Magi. Anders has made several attempts at escaping the tower and done so successfully but would quickly be re-captured due in part to the Templars possession of his phylactery (vial of blood) but more largely because of the grudges held against him by women whom he has been in past relationships with.
Unlike most mages seeking freedom from the tower Anders has never resorted to blood magic but the Templars have labeled him as such anyway. He was once held in solitary confinement for a year and within that time the only companionship he had was that of Mr. Wiggums the cat that lived in the tower. Mr. Wiggums was eventually possessed by a demon and took out four Templars before he was slain lending to Anders love of cats.
During his seventh escape attempt Anders took refuge from a dark spawn attack in the Warden’s tower, displaying amazing fighting capabilities. He was soon recognized by the Templars who intend to kill him instead of risking another escape attempt but the Grey Wardens recruit him much to the Templars dismay. During his time with the Grey Wardens the Commander gave Anders a cat he named Sir Pounce-A-Lot after hearing of Anders time in the tower and assisted Anders in destroying his phylactery.
After a time Anders was forced to leave his cat Sir Pounce-A-Lot with a friend in Amaranthine because the Warden commander thought it made him soft. Justice, a spirit from the fade who had assisted the Warden and befriended Anders was living an unnatural and distressing life in the mortal world where it did not belong. Seeking to aid his friend Ander's allowed Justice into his body. The merge made Anders mellower, more focused on the tasks before him, and more invested in seeking freedom for all mages. He eventually "left" the Wardens by sneaking off and going into hiding. Ander's started up a free clinic in Kirkwall and befriended the Champion of Kirkwall.
Ander's hatred for the Templars and the injustice endured by the mages tainted Justice who gradually became violent, merciless, and hostile which changed him from a spirit of Justice to a spirit of Vengeance. When angered, Anders body is taken over by Justice who struggles to tell friend from foe and kills indifferently, even the mages or people their trying to save. Anders comes to believe that what he did with Justice, however good intentioned was crueler than the alternative. With his control of Justice slipping farther away each day, Anders fell into a depression believing himself to have committed the same wrongs as blood-mages with Justice now as uncontrollable and ill-natured as a demon.