Count the Shadows

"Count the Shadows" is the sixth episode in the eighth season of Doctor Who, set on the gothic planet of Gregorae, which has become infested by Vashta Nerada, led by the Father of the Hive.

Synopsis
The Doctor, Billy, and Isabella arrive on the planet of Gregorae, once a thriving gothic metropolis, but now seemingly abandoned. Soon they come face to face with the Vashta Narada, and the Doctor fears that something went terribly wrong on Gregorae. Led by the Father of the Hive, a human host infested with Vashta Nerada, the shadows reveal the dark tale of the fall of Gregorae at their hands, and the similar fate that awaits the Time Lord and his friends.

Vashta Nerada
The Vashta Nerada infestation on Gregorae is far more dense than that of the Library (Silence in the Library, Forest of the Dead), they are led by a Hive Leader, the Father, a human host infested by Vashta Nerada.