Our Mother IV was the queen of a race of genetically altered intelligent giant termites. She was constantly giving birth, and claimed to retain memory of all of her offspring.
Later in her life, she attempted to take over Valhalla, with the goal of selling the humans into slavery, but was foiled by the Seventh Doctor. She died soon after this attempt, and it was assumed that she would be succeeded by Other Mother V. (AUDIO: Valhalla)