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Anders is a fugitive mage from the Dragon Age series. He's a companion of Hawke, who plays a major role in Dragon Age II.
His goal is to make all mages free from control of the templars and he is ready to achieve this at all cost, including propaganda, manipulation and terrorism. He calls keeping mages controlled by templars a slavery, however he approves of enslaving Fenris again, likely enjoying the irony as Fenris wants the mages "enslaved". He often views those who oppose his cause or seek a diplomatic alternative as his enemy or an obstacle. One of the few things he has in common with the Templars is his contempt for blood mages and people who willingly work demons. However along with these mages he often blames other factors more than the mage themselves feeling that many of them did so out of desperation because of the general treatment of mages, Huon is a perfect example.
He shares his body with a demon of vengeance, which was originally a spirit of justice but when they decided to merge Anders' anger towards the Templars accidentally corrupted Justice, Justice/Vengeance's more aggressive and vengeful behavior in turn makes Anders' more aggressive and irrational.
In the end of the game he nukes Chantry killing everyone inside and he didn't care he killed someone close to another companion Sebastian. Hawke can spare him or execute him. If the former is chosen then he can either fight for his cause or be persuaded to fight against it.