Wilberforces are slug-like creatures featured in the book and TV series as well as the film Under The Mountain. Wilberforces originated from an unnamed planet with oceans of mud and continents of stone. There were only 2 inhabitants; One of them were the Wilberforces and the other was a species of battleship sized, blind, mouthless worm. The Worms absorbed the mud through their stomachs. Both species were near extinction but managed to escape from planet to planet. They then entered Earth's New Zealand and tried to turn the planet into mud but were stopped by the heroes of the book, Rachel and Theo, killed the Wilberforces and the Worms, causing a local volcano to erupt. The life form who trained them to defeat the Wilberforces, Mr Jones, "dies" soon after but is then seen rocketing into the sky.