A Human male, Y'ull Acib was a hardened criminal and had been condemned to serve out a prison sentence in the spice mines of Kessel by the Galactic Empire. Meeting fellow criminal Fliry Vorru while working in the mines, both prisoners, along with fourteen others, were released by the New Republic and sent to Coruscant following the capital planet's liberation from the Empire.
The Republic's strategy, developed by war hero Wedge Antilles, was to release the prisoners into Imperial City and have them to wreak havoc for any remaining Imperials that were hiding out or trying to control parts of the city. While the plan was deemed a success, the prisoners remained free and dangerous long after the last Imperials were driven off. Working closely with his ally Fliry Vorru, the last of the line of criminal Underlords, Acib set to work on reestablishing the power of the infamous crime syndicate Black Sun.
In the wake of the Imperial Grand Admiral Thrawn's death, Acib succeeded in mustering the strength of the Undercity's meanest criminals and Black Sun was revived. Declaring himself Underlord, the leader of Black Sun, Acib ruled with vigor and quickly amassed more and more power. In an effort to avoid assassination or treachery, Asib cloistered himself in a clandestine location, rarely appearing in person and conducting all meetings via hologram communication.
Following the final death of Emperor Palpatine in 11 ABY, Acib made an alliance with Grappa the Hutt in an attempt to gain control of the Imperial Interim Ruling Council. To achieve this, Acib ordered the successful assassinations of Councilmen General Immodet and Xandel Carivus. At Grappa's urging, Acib planned to clone Carivus and replace him, the other councilmen none the wiser. Assembling the clones on Ord Cantrell, the Imperials discovered the deception and had all of the clones executed. Discovering Black Sun's involvement, the Imperials became enraged with Black Sun and began to hunt for Acib; in turn, the Republic discovered the cloning facility which had been used, owned by Macus Kayniph, and destroyed it.
Believing Grappa a failure, Acib's fears were realized when the Hutt was captured by Zanibar mercenaries and taken to Xo as part of a ritual sacrifice. After suffering such a devastating blow, with the Imperial's enraged and the New Republic in hot pursuit, Acib was easily overthrown in 12 ABY by Durga the Hutt. Claiming the title of Underlord for himself, Durga went on to control the syndicate.
- Star Wars Handbook 2: Crimson Empire
- The Essential Chronology
- The Official Star Wars Fact File92
- The New Essential Chronology
- Star Wars: The Comics Companion
- The Complete Star Wars Encyclopedia