"I underestimated you, Warden. I thought you were like Cailan, a child wanting to play at war. I was wrong. There’s a strength in you I’ve not seen anywhere since Maric died." ―Teyrn Loghain Mac Tir to Aedan, upon being defeated
Darkspawn sensing: Aedan is granted this ability due to the darkspawn taint in his blood. After undertaking the Joining ritual, he is able to sense the presence of darkspawn and other Grey Wardens by sensing the taint in their blood, helping them to detect hidden darkspawn. Thus, he has the ability to hear the thoughts and words of the Old Gods and those controlling the darkspawn, such as Archdemons. While the taint does give the Grey Wardens the ability to better hunt darkspawn and their leadership, it also gives them wild and horrifying dreams at times and, eventually, will kill them by driving them mad.
Power of Blood: After drinking the Alchemical Concoction made by Avernus, Aedan’s powers gained from the darkspawn taint are "enhanced", making him grow even more powerful than he was before. The amount of corrosive blood he can spit from his mouth can melt almost anything in its path. He can anoint his weapon with the same toxic gore, making it as lethal as any natural or man-made poison.