Vayla was the leader of the Elystrians for several hundred years.
Vayla met the Doctor upon his first visit to Elystria. He developed the Elystrian robots to perform menial tasks in the place of the Elystrians. However, the robots overthrew him and imprisoned him. The few survivors of the onslaught blamed Vayla for it as they believed he controlled them. The Fourth Doctor freed Vayla from the stronghold in which he was imprisoned and Adric disabled the robots with a co-ordination control. Sklar helped the weak Vayla away from the stronghold, telling the Doctor he was to be reinstated as leader. As Elystrians are leader for life, he presumably ruled until his death. (PROSE: Planet of Paradise)