PYROVILE

Planet of origin: Pyrovilia

The Pyrovile is a alien species that evolved on Pyrovilia. They are made of stone held together by living magma. They had developed space travel more than 2000 years ago when they lost their homeworld. They are very fragile to water exposition since it causes their magma to cool.
One of their survivor ships crashlanded in Italy, shattering them into dust. In 62 AD an earthquake which reawakened mount Vesuvius re-awakened them, and under gaseous form, they started possessing human hosts and planned to terraform Earth to make it more like Pyrovilia through the use of an energy conversion matrix. On Earth, they assumed a shape resembling that of giant roman gladiators but it remains unknown if this is their true form or if this likeliness was linked to the possession of humans. They were all destroyed in the AD 79 eruption of Mount Vesuvius.

ADIPOSE

Adipose are a sentient bidpedal species that developed a space faring civilisation whose body is mainly composed of fat.

Their natural mean of reproduction remains unknown but when their breeding world became unfit for use in the early 21st century, they enlisted the service of alien agent to have their birthing matrix implanted in humans through ingestion. Each matrix was building an adipose baby from large fat deposits contained in their overwieght human hosts. The baby was then extracting itself from fat mass with minimal harm done to the host. Adipose babies are notorious for their precocious motor autonomy. As soon as they are born they are able to walk with an overall good sense of orientation and purpose.
Source: Doctor Who "Partners in Crime"