Isolus

The Isolus were tiny empathic beings which resembled white flowers with streaming tendrils. They travelled via solar winds.

Biology
Isolus were originally born as spores by their mothers. These Isolus would travel through space in heat-powered pods and would grow for thousands of years until they reached their adulthood, and, in order to pass the time, used their ionic power to project fantasy worlds to play in. The ionic power of an Isolus to create these virtual worlds could also bring inanimate objects, such as drawings, to life, as well as transform living things into drawings. These young Isolus also required strong emotions, specifically love, to survive. Isolus travelled in groups of around 4 billion and required constant companionship to feed off the love of their siblings. (TV: Fear Her)

Abilities
Young Isolus could create objects and worlds out of their own imagination, and play in these worlds as they travelled through the void of space. If a family of Isolus left an area, anything they changed would return to normal quite quickly, but something they created would linger for a few minutes, especially if it was strongly related to an individual, Isolus or not, who still resided in the area.

One way Isolus were seen using their powers was by converting a work of art into an actual, existent being, or vice versa. This artwork could move around as it could before being transformed, but couldn't make noise and therefore had to gesture or write to communicate. Use of their power produced large amounts of iron residue as a by-product. (TV: Fear Her)

History
In 2012, one Isolus was separated from its siblings after a solar flare. It landed on Earth on 21 July, and searched for heat and a friend. It was able to find Chloe Webber, another lonely child. Chloe swallowed the Isolus and the spore granted Chloe its ionic powers, using them to trap other children in drawings in attempt to feel less lonely. On 27 July, it trapped the Doctor and the TARDIS, but Rose Tyler quickly managed to retrieve its dead pod and recharge it by throwing it into the Olympic Torch. The Isolus left Chloe and released all of its victims. It's pod was launched back into space to meet up with its family when the Doctor lit the Olympic Flame. (TV: Fear Her)

Behind the scenes
Russell T Davies originally intended to have the Isolus, along with many other alien races from throughout the entire series, appear in the Shadow Proclamation scene in The Stolen Earth. This was scrapped due to time limitations and the scene ran with just the Judoon and the Shadow Architect's people.