Dark Prince, Dark Lord.
Xizor was born the scion of a wealthy royal family on Falleen. Head of Xizor Transport Systems and already a trillionaire during the last years of the Galactic Republic, his extravagant tastes were evident from an early age. He made his presence known on the planet of Coruscant by erecting an enormous palace in the middle of the cityscape, east of the Presidential Palace. The massive undertaking required the former Farfalla skyscraper razed down to its subfoundations. After the rise of the Empire, Falleen was home to a biological weapons laboratory that worked on secret projects for Darth Vader. In 7 BBY, a flesh-eating bacterial agent was accidentally released from the bioweapons lab, causing Vader to order the lab, and the surrounding city, to be razed to prevent an outbreak and keep his projects secret. Xizor's father, King Haxim, was the ruler of the local region, and his parents, brother, two sisters and three uncles perished in the orbital bombardment. Xizor was off-planet at the time, cementing his position as a Vigo in Black Sun. Upon his return, he had virtually all knowledge of his position destroyed. He planned revenge on Vader but didn't want knowledge of his personal vendetta made public.
In the years that followed, Xizor built two concurrent empires: one legitimate, one criminal. Xizor emerged as the leader of Black Sun and the proprietor of several major galactic corporations. To fund and facilitate his illegal empire, Xizor had his legal firms, such as Xizor Transport Systems, funnel funds, transfer contraband and launder millions of credits. Xizor was driven by his desire to restore his opulent lifestyle and to destroy Darth Vader. To disguise his planned revenge, Xizor used his connections to remove all record of Vader's involvement in the death of his family. Everyone assumed their rivalry was jockeying for favor from Emperor Palpatine, who subtly encouraged the rivalry.