Rakszan is a Necron Lord, and is the only surviving member of the Khansu Dynasty that had been destroyed during the War in Heaven. After betraying his people and leading them to biotransference, the dynasty’s subsequent destruction and separation after the great conflict changed Rakszan, and he now has embarked on a personal mission to see every remaining fragment of C'tan caged for all of eternity.
When the Necrontyr race began the process of biotransference that would turn them into the soulless Necrons, by no means did all of the Necrontyr people go willingly to the chambers of transformation. However, the nobility of the Khansu Dynasty fought the onset of biotransference more than most, and at every turn. When it became clear that no amount of political manoeuvring or manipulation could prevent what was to come, the Khansu Dynasty fought in armed revolt against the dictates of the Triarch. Yet one Phaeron, no matter how powerful, could not hope to fight the rest of the dynasties and their C'tan masters.
Ascendant Prince Rakszan was one of the few Necrontyr nobles amongst the Khansu Dynasty to choose biotransference of his own volition, and he cursed his people for their foolishness in resisting what could be a new age of glory. For his loyalty to the Triarch, Rakszan was granted high military rank and his first campaigns were those that brought his rebellious kinsmen to heel. One by one, Khansu's coreworlds fell, the crownworld of Hamun last of all, and those few rebels that survived were dragged to the chambers of transformation.
At first, Rakszan was pleased, for his people would now have the chance to regain the honour lost in revolt against the Triarch. Yet, as the War in Heaven ground on, he witnessed the C'tan and their underlings systematically destroying his dynasty. Indiginity was added to defeat, with the Necrons of the Khansu Dynasty deployed at the forefront of every battle, or else dispatched on campaigns where there was little hope of success and none of survival. Little by little, Rakszan came to realise the terrible depths of his mistake. When the Necron rebellion against the C'tan began, none fought so hard as he to see the Star Gods toppled.
By that time however, the Khansu Dynasty was lost forever, its nobles destroyed in the War in Heaven, its Necron Warriors and Immortals seized by other dynasties and reprogrammed to their service. In all the galaxy, only Rakszan remained to speak for his slaughtered kin, and he held himself a traitor to their memory. With no other way remaining to atone for his betrayal, Rakszan swore that he would see every surviving fragment of every C'tan caged, so that they could never again arise. It is a quest that continues to this day...
- Codex: Necrons (5th Edition), pg. 12