Alien (Devil in the Smoke)

An alien being came to Earth in the 19th century and was stopped by Vastra, Jenny Flint, and Strax.

The alien took over the corpse of Able Hecklington and threatened to blot out the sun of Earth. While using the form of Able, the alien force killed Harry. It was eventually defeated by being doused in snow. (PROSE: Devil in the Smoke)