Family of Blood

The Family of Blood was an incorporeal, green group mind. Because of their lack of form, they required a physical body to inhabit. They only had short lifespans. (DW: Human Nature)

Technology
They were one with their spaceship, which had the ability to turn invisible, protected by a green shield. They could also animate different things for servants (in the case of their 1913 invasion of Earth, scarecrows), although whether this was another feature of their group mind is unknown. (DW: Human Nature)

History
At somepoint in their their history they encountered the Doctor and Martha Jones and chased them for Time Lord near-immortality, as they only had short lifespans. The Doctor was forced to turn himself Human using the Chameleon Arch to escape them, and was disguised as a teacher at a boy's school in England in 1913. (DW: Human Nature)