Strange matter

Strange matter was a substance that was the result of or could create spacio-temporal anomalies. (PROSE: Spiral Scratch) Strange matter was very dense. Small pieces could weigh as much as a planet. Colliding two pieces of strange matter could create a time manipulator. (TV: Time and the Rani)

Manipulating strange matter
The Rani attempted to discover the secret of manipulating strange matter on the planet Lakertya through the use of several intelligent beings including the Doctor (who had recent regenerated into his seventh incarnation). The Rani ultimately discovered the key to manipulating strange matter, but was prevented from implementing her ideas by the Doctor's intervention. (TV: Time and the Rani)