Erasmus Darkening

Erasmus Darkening was an alien scientist who came to Earth in the 17th century.

In the 17th century, Erasmus Darkening posed as a magician and alchemist to get shelter from and employment by Lord James Marchwood. Over the course of what the legend stated to be two years, Darkening used advanced technology to open a portal between dimensions to get home. Innocent people were caught in Darkening's experiments and trapped between the dimensions; they were afterwards sighted at times and thought to be ghosts haunting Ashen Hill Manor.

After Marchwood's two children fell victim to Darkening's experiments, and enraged Marchwood attacked Darkening in his laboratory and impaled him with a sword. This act damaged Darkening's accelerator; the device became powered by the people it took and channelled their life energy into Darkening, granting him immortality.

Darkening became obsessed with his immortality, and began to call the Manor his dominion. Marchwood confronted him again, and tricked him into stepping into a electromagnetic field, ending his existence whereupon by stabbing his sword into the metallic floor engraving of the Marchwood family seal, which channelled the energy into it and trapped Darkening inside to be destroyed. His last words were, "Eternity... I've lost eternity!" With Darkening vanquished, Sarah Jane Smith disabled his device once and for all.

_{Biography from the TARDIS Data Core article, licensed under CC-BY-SA}