Krillitane

The Krillitanes are a composite race who absorb the physical traits from other species they conquer. By the time of their incursion on Earth in 2007, they were far more gargoyle-like in anatomy, having acquired their wings from the people of Bessan.

Biology
As a composite race, the Krillitanes undergo radical anatomical changes over the course of generations, as they assimilated biological traits from other species they conquer. In their most recent Bat-like form, they demonstrate highly sensitive hearing and a preference for sleeping upside-down on ceilings. They are also carnivorous, having been documented eating Rats and even Humans. However, due to their unstable genetic structuring, Krillitane Oil is highly toxic to them, causing a caustic reaction upon contact.

History
According to The Doctor, the Krillitanes resembled Humans with "really long necks" the last time he encountered them.

A group of 13 Krillitanes arrived on Earth in 2007 and disguised themselves as Human school staff with the use of morphic illusions, infiltrating and taking over Deffry Vale High School. During this time, they secretly imbedded Krillitane Oil in the food served to the pupils to enhance their intelligence. Using the children's augmented intellect and intelligence in combination with an advanced computer network, the Krillitanes sought to solve the Skasis Paradigm, the theoretical equation behind creation itself, and so gain power over the universe as a result. Although initially tempted to share in this goal, the Doctor, along with three Human companions and a dog-like robot called K-9, put a stop to this plot. K-9, at the cost of its own destruction, detonated the Krillitane Oil and the school once it was evacuated, killing every Krillitane inside.

Appearances

 * Doctor Who, series 2, "School Reunion" (2006)