Q is for... Queen Bats

Creatures which inhabited the planet Androzani Minor, they resembled terrestrial bats but were the size of a man. They nested in structures composed of raw spectrox - a substance which could only be found on this world. The bats were immune to the substance, whereas mammalian life developed a disease called Spectrox Toxaemia. This was fatal to humans and Time Lords alike, but a scientist - Professor Jackij - had previously discovered that the milk from a Queen Bat could provide an antidote.

The Doctor and companion Peri Brown contracted the illness after she fell into one of the nests, and he helped her remove the adhesive spectrox strands.

The rebel scientist Sharaz Jek, who had previously held the pair prisoner, informed the Doctor of the antidote when he learned that both were dying. The Queen Bats had retreated to the lowermost galleries of the planet to die, a region with very little oxygen. The Doctor risked his life to descend to their lair, despite an imminent scalding mud-burst threatening to erupt.

There was only sufficient milk for Peri, and the Doctor was forced to regenerate.

Appearances: The Caves of Androzani (1984)

• The visual effects team were very unhappy that the Queen Bat was hardly seen on screen, after spending so much time working on it.
• The head was later sold at auction: