Haemovore time stream

In one timestream which was a possible future relative to 20th century Earth, the Haemovores evolved from humans, having been mutated by the chemical slime of a polluted Earth. This time stream was accessible to time travellers. (PROSE: Goth Opera, TV: The Curse of Fenric)

The Haemovores evolved on Earth circa 500,000 AD, after the planet was ruined by industrial waste. They lived under the chemical swamps, in the saline solution of the ocean, consuming plankton and sometimes ganging up on a great whale to feast. (PROSE: Goth Opera) The last Haemovore was Ingiger, who believed himself the last living creature on Earth. Fenric brought Ingiger back in time to Transylvania some time after the 10th century, where he fed on the Vikings who had taken the flask containing Fenric. (TV: The Curse of Fenric)

Behind the scenes
History of Mankind according to Doctor Who claimed that the Haemovores were a part of the familiar, linear timeline of the Doctor's universe, placing their existence on a polluted Earth abandoned by humanity between the years 5000 and 10,000. It is further stated that the Haemovores went extinct as the planet's ecological balance was restored, leaving it to be reclaimed by humanity.