The Endovorms — who had the appearance of stone lions — were used by the Sevakrill to guard Nelson's Column while they prepared a missile inside it. The Endovorms were made invisible by perception filters to anyone from that time. While the Fifth Doctor climbed the column, they tried to kill Tegan Jovanka and Nyssa. The Endovorms killed seven civilians and a policeman before the Sevakrill were cast out. They then returned to their plinths and when their filters ran out after a few decades, Edwin Landseer unveiled them as his own creation. (PROSE: The Lions of Trafalgar)