Pyrodines were fire-like creatures. Morjanus created them primarily because they were immune to psychic attacks. Her people were fighting the Hunters, a psychic species, so this was a treasured attribute.
In London, in 1840, the Pyrodines were released from gaslights by a proto-morphic lifeform under the command of Morjanus. They killed a policeman called Bates. Morjanus intended that they should burn the city to the ground, but they disappeared when the proto-morphic life form was destroyed by the Eighth Doctor. (COMIC: The Curious Tale of Spring-Heeled Jack)