Doctor Who and the Horns of Nimon — Terrance Dicks

In the great maze of the Power Complex dwells the dreaded Nimon, a fearsome monster with immense scientific powers.

The Nimon has promised to restore the Skonnan Empire to its former Glory. But first it demands sacrifice - youths and maidens from the peaceful planet Aneth.

The Tardis collides with the space ship delivering the victims, and the captured Romana is condemned to be sacrificed to the Nimon.

Aided by the faithful K9, the doctor goes to the resuce. In the heart of the maze he confronts the Nimon and uncovers the terrifying plot to enslave the galaxy.