Kassia

Kassia was a Consul of Traken.

Biography
Unlike her fellow Consul and husband, Tremas, Kassia was a "gifted sensitive" and so represented a different constituency than him. Since her youth, she had been assigned by the Keeper to tend to a Melkur in the Grove. Over time, she became infatuated with it.

As a part of her wedding blessing, the Keeper decreed her new stepdaughter, Nyssa, should take over the duties. Because of her strong connection to the Melkur, however, Kassia continued to seek the Melkur's company. During one such visitation, Kassia revealed that Tremas had been named as the Keeper's successor, which meant she had to leave him, and the Melkur began to speak to Kassia. Unbeknownst to her, the "Melkur" was in fact.

The Master used Kassia's feelings toward the Melkur for his own purposes, and used her (with the aid of a band around her neck that placed her under his control) to orchestrate an elaborate coup. At the insistence of what she believed from the Melkur, she killed and manipulated her way into the Keepership itself — even though her actions estranged her from Tremas.

Since the Master needed to become Keeper himself, he killed Kassia as soon as she ascended to the Keeper's chair. She never reconciled with either Tremas or Nyssa, (TV: The Keeper of Traken) although Nyssa would later lament the loss of her step-mother, as well as the death of Tremas and the destruction of Traken. (TV: Logopolis) Ironically, far from 'saving' her husband, Kassia's actions would ultimately lead to Tremas's demise, as the Master would later hijack his body shortly after her death.

Behind the scenes
Francesca Annia, Judi Dench, Glenda Jackson, Joanna Lumley, Helen Mirren, Diana Rigg and Fiona Walker were considered for the role before Sheila Ruskin was cast.