Kraytos was approximately 12 feet tall, weighed 650 pounds and could move a 1.7 metres per second.
Kraytos' tribe had been battling Tumat's Ha'loss tribe for thousands of years as their technology got progressively more advanced. Finally, a quantum bomb was created to end the battle, with Kraytos and Tumat being the only two survivors at the centre of the explosion. This caused their atomic structure to change, being thrown outside of reality as they continued their battle. Now immortal and with their bodies reflecting all energy that hit them, they rematerialised one million years later to fight on Gatan.
Capitalising on this, their fights were filmed by The Freedom Thoughtcasting Network (FTN) on The Eye Above, run by Berakka Dogbolter, with Sandola Dell providing a commentary. This was used by Berakka to become rich by forcing the trillions of viewers to pay to view, while also creating merchandise and advertisements based on them. The City of Radiant Stone was devastated by their battle, and although they arrived on Gatan less than half a year ago, people thought that they had been fighting for a long time.
They were encountered by the Thirteenth Doctor, Graham, Yaz, and Ryan when they intended to visit Gatan's "party era", but saw the city destroyed instead. They met a young girl called Tondi who had lost her mother in the attacks, and Yaz worked to try and find her while Graham and Ryan scouted the area and the Doctor discovered what was going on. With everyone but Yaz being teleported to the FTN, the Doctor learnt Kraytos and Tumat's history and eventually used Graham, in costume as Tumat, to lure Kraytos to a teleportation pad. The Doctor teleported the two into the same space, becoming one creature that the Doctor dubbed 'the Chimera'. With him finally understanding the pain and suffering caused from both warriors, the Chimera resolved to change his ways and, after the Doctor shut down the thoughtcasting, teleported away on good terms. (COMIC: The Warmonger)