Alessa is a human who lives in Kirkwall.
When Hawke goes to search DuPuis' estate during the quest Prime Suspect, they eventually find Gascard DuPuis with a woman named Alessa. Gascard begs Hawke to spare him, claiming that several years ago his sister was killed by the true murderer who now roams Kirkwall. He moved there to avenge her, and took Alessa hostage since she was the next victim. When Alessa claims Gascard hurt her, he explains he only took her blood in order to be able to trace her thanks to blood magic, should she be abducted. Not wishing to remain with him, Alessa flees for her life out of the estate, with Gascard fearing that she will link him to the murders.
Later in the quest All That Remains, Hawke will find Alessa's body in Quentin's hideout in the basement under the foundry in Lowtown, her hair mysteriously bleached. Quentin also causes Alessa to appear in the possessed form of a desire demon which Hawke must destroy, along with Ninette de Carrac and Leandra Amell.