Altos was a young dark haired man sent by Arbitan to find the keys to the Conscience of Marinus. Instead his friend Eprin and he were enslaved in Morphoton thanks to power of the Mesmeron. As a Morpho's slave he welcomed Barbara in the city, offering to grant her every wish. He did the same with Susan and the First Doctor, who respectively asked for a fancy dress and a complete visit to the laboratories. He assented to both their requests. Ian did not trust him because his eyes never blinked during the conversation. When Barbara proved herself resistant to the power of the Mesmeron, the Morphos ordered Altos to kill her. He tried to strangle her but Sabetha hit him over the head with a stool. He collapsed.