Mim

The Mim are a race of purple sponge-like beings native to a planet known as the Mim Sphere.

Biology
The Mim are mostly made up of nervous tissue. (AUDIO: The Wake) They had purple, tentacled sponges and the ability to take on the shape of humans and Time Lords. (AUDIO: Shadow of the Past)

History
The Mim were responsible for the destruction of the Library of Alexandria. (AUDIO: The Library of Alexandria)

One Mim came to the Earth in the early 1970s as an advance scout, while the rest of the fleet waited in orbit near the Earth. They wished to take over the Earth to use as a breeding planet. The Mim that landed on the Earth was locked in UNIT's Vault 75-73/Whitehall and started to take the form of Sergeant Robin Marshall. (AUDIO: Shadow of the Past)

The Eighth Doctor and Lucie Miller once saved some Mim delegates on Northern New Mars. (PROSE: The Great Escapes)

The Mim fought a war with the Draconians at the start of the 27th century. (PROSE: Nobody's Children) The Mim were seen as a credible threat to the Braxiatel Collection. (PROSE: Parallel Lives)

During the war against the Draconians, Draconian ambassador Kothar revealed that he intended to get the courts to argue the the Mim were non-sentient, thus allowing the Draconians to use a slew of new weapons otherwise prohibited by law. (AUDIO: The Judas Gift)

Their home planet, the Mim Sphere, was destroyed by Hass. After being manipulated into it by Irving Braxiatel, he used the built up radiation stored in his pressure suit to destroy the planet. (AUDIO: Freedom of Information)