Kroton (species)

Evolution
The Krontons evolved from predatory grasi-organic tellurium based crystal on the planet Krosi-Apsai-Core, they could mimic their prey's abilities. At some point in their history they encountered a human servo robot and thus attained semi-sentience.

As they evolved they became semi-sentient amoured crystalline beings which fed on / psychologically linked to mental vibrations.

Recent History
The Kroton Absolute are overseen by the First Lattice, originally a fortress on the Kroton's home world, it contains the four highest brains in the Kroton Absolute.

The First Lattice was moved from the Kroton home world when the war began with the Metatraxi, it took over four thousand Krontons to lift the First Lattice into orbit and it had exhausted all of them.

The Krotons have crystalline bodies which can be broken down and reformed to suit the environment and the situation which they are in. (EDA: Alien Bodies)

Encounters with the Doctor
The Krontons have encountered the Doctor on three occasions.

On one occasion the Doctor killed a pair of Krontons stuck on a planet of humans known as the 'Gonds', he assisted in their destruction through the use of chemistry. (DW: The Krotons)

On a second occasion a Doctor with curly hair and a bright coat encountered a dynatrope with at least 4 Krotons on board and assisted a group of humans again to destroy two of the Krotons, though he did allow the remaining Krotons to escape.

The third encounter was on Earth during the auction of The Relic, the Kroton Absolute intercepted a Dalek cruiser on its way to the auction and sent a Kroton on the Dalek ship. The Doctor that was at the auction was unaware at first of The Relic's origins. (EDA: Alien Bodies)