Who is Aspen from Tehanu: The Last Book of Earthsea and what is their importance?

Aspen is a wizard. He lives in the Lord of Re Albi's house, and it is rumored that he was brought to Re Albi to help the old man live forever. The rumor circulating in the village, in fact, claims that Aspen is using the life force of the old man's son to keep him alive. Tenar and Aspen have two confrontation that end with Aspen cursing her. The curse results in Tenar losing the ability to think for herself. Tenar leaves Ogion's home to escape the curse, but later returns to see to Moss's health. It is at this time that Aspen reveals his true evil side and takes Tenar under his control. Aspen wants to rid the world of the good wizards and good people, as their absence will make it easier for him to rise up and take control. His scheme comes to an end when Aspen and his friends are killed by Kalessin.