The space eels were a race of intelligent, eel-like creatures.
The space eels were so named because they resembled eels. They left a trail of slime when they moved and were capable of devouring a cat. They were also able to be transplanted into humans, giving them complete control of their bodies. (AUDIO: Ashenden)
The space eels sent out a signal into deep space which was detected by Professor Sidney Ornadel and Isla Satterthwaite at Ashenden. Miss Satterthwaite solved the eels' puzzles, unwittingly giving them information on Earth and humanity's capabilities, and they helped her produce the Ashenden Formula to model the ideal population of the United Kingdom with reference to density, makeup and infrastructure. They then sent her equations equal to the size of Ashenden.
When the Department of New Towns told Miss Satterthwaite to find a way for the eels to communicate with them, one transplanted itself into her and became their sole spokesperson for a time. They worked to create the perfect society at Ashenden, planning to travel through a rift to possess the people there, and culled those that they deemed undesirable. They chased Norton Folgate when he left Ashenden, also possessing Gideon Lyme and the Torchwood Emergency Continuity Board who confined Lizbeth Hayhoe and Andy Davidson to Pinkerton's Lodging Rooms when they appeared.
The space eels were defeated and returned to their planet when Lizbeth and Andy served as a time cone converter when the rift was opened. The paradox that the two humans created snapped the rift shut, restoring some of the people that they possessed whilst others were left hollow. (AUDIO: Ashenden)