Sharlan

 was a scientist of the planet Ashtallah. Along with Brenna, they were fascinated by all of the concepts brought to the planet with the arrival of the First Doctor, Susan Foreman, Barbara Wright and Ian Chesterton. Though not all to familiar with the idea, they believed themselves to be in love with Brenna. They used a sample of Barbara's blood on other Ashtallans as an experiment, in spite of it leading to them dying, wanting to increase their ambitions with the idea of a shorter lifespan after seeing the Doctor's TARDIS.

They didn't believe what they were doing was wrong, as they were unable to comprehend death. Together with Brenna, they used genetic material from each other to create a child with the Doctor's help. When their child was in danger of dying itself, Sharlan got themselves infected with the plague to protect it, succumbing to the illness. Brenna mourned their death. (AUDIO: The Invention of Death)