Oksanna

Oksanna was a living plant. She lived in a giant, greenhouse-like dome on Titan. She was a mistress to the great tree monster who lived in the ground and helped him to take the Twelfth Doctor, Bill, Rudy Zoom, Lady Takashi and the rest of Zoom's ship's crew.

Oksanna was in fact Lady Takashi's mother, killed in her sleep by the tree monster. She helped the Doctor and his friends to escape and perished in the explosion that destroyed the dome, along with the rest of the creatures. (COMIC: The Soul Garden)