Thane Krios is a fictional character first seen in Mass Effect 2. He is 39-year-old drell assassin who is dying of a disease known as Kepral's Syndrome, exclusive to drell. He is encountered on the asari-dominated world of Ilium.
Raised on the hanar homeworld after the hanar saved the drell from extinction, Krios was trained as an assassin from the age of 6, making his first assassination at age 12. He met his wife, Irikah, during an assassination mission when she stepped in front of Thane's target in order to stop him. After eventually marrying Irikah, the hanar allowed Thane to stop doing assassinations for them to raise a family, but realizing he had no other skills, became a free-lance assassin, keeping it secret from everyone but his wife. Thane's wife was eventually murdered by mercenaries attempting to capture him. Heartbroken, Thane tracked down and killed each of the mercenaries responsible.
Thane returns in Mass Effect 3 if he survived the events of Mass Effect 2.