Gathering in swarms many thousands strong, the Vashta Nerada are microscopic beings living mostly in the dark and appearing in the light as a shadow cast by nothing.

Their name means 'Shadows that melt the flesh' – a large swarm of Vashta Nerada can strip the flesh from a creature in milliseconds. Existing on over a billion planets including Earth, they inspire a fear of the darkness in most species – any shadow could contain a swarm of Vashta Nerada.

The Tenth Doctor believed they have no weaknesses and the only defence against them was to stay away from shadows or to run...