Mira (The Fires of Pompeii)

Soothsayer is a member of the Sibylline Sisterhood that were in Pompeii in 79 CE. She has eyes painted on the back of her hands - a sign of a soothsayer. She was the first of the Sisterhood to see the TARDIS or "Blue Box" that had appeared in a prophecy. She had psychic powers due to breathing in dust from Vesuvius that was converting her into a Pyrovile and could see time thanks to the rift activity there. It is likely that she died during the eruption as it has not been shown otherwise. (DW: The Fires of Pompeii)

Behind the scenes
Actress Karen Gillan was later cast as Amy Pond, first companion of the Eleventh Doctor played by Matt Smith beginning in Series 5. This is the most recent example of an actor being cast in an ongoing role in Doctor Who after making a one-off guest appearance as another character, similar to Freema Agyeman's one-off character Adeola Oshodi before her appearance as the Doctor's companion Martha Jones and Eve Myles's character Gwyneth on Doctor Who, before her starring role on Torchwood as Gwen Cooper.