The Eleventh Brother was a Force-sensitive Zabrak male and Imperial Inquisitor serving the Galactic Empire.
Not much is known about the Eleventh Brother's early life, such as his place of birth, or even his true name. However, it is known that he, like many of the Imperial Inquisitors, was a former Jedi that turned to the Dark Side, having abandoned the Jedi even before Order 66.
Serving the Imperial Inquisition
The Eleventh Brother was taken into the Imperial Inquisition after displaying a natural affinity for the Dark Side of the Force. Seen as promising by Darth Vader, he quickly established himself as a powerful force in combat, taking pleasure in inflicting fear and pain upon others. The Eleventh Brother was often paired with the Twelfth Sister, with the two making for a fearsome duo, despite their conflicting personalities.
Mission to Nirakos
The Eleventh Brother was sent to the planet Nirakos with a small detachment of Purge Troopers in 4 BBY to eliminate the exiled Jedi Master Kira Cereza. He was sent without the Twelfth Sister as it was deemed his skills should be sufficient on his own to deal with the Jedi. Landing at the small village where Master Cereza was hiding, he ordered the Purge Troopers to raze the village in order to draw the Jedi out of hiding. The plan worked, and Master Cereza came out to confront him and his Purge Troopers. After dispatching the Purge Troopers, Master Cereza then engaged the Eleventh Brother in a lightsaber duel.
The Eleventh Brother proved to be more than a match for the aging and weakened Jedi Master, who had fallen out of form due to her years in exile. The Eleventh Brother managed to best Master Cereza and and prepared to strike her down, whereupon her young Padawans, Ral and Ren Silber, came out in an attempt to stop him. Noticing the two other Force sensitives, he dealt the finishing blow to Master Cereza before turning his attention to her students. Ral then engaged the Inquisitor in order to protect her younger brother, but was ultimately bested as well, being killed in short order. However, Ren proved to be much more powerful, taking his fallen sister's lightsaber and lashing out with fury. Being taken by surprise, the Eleventh Brother was forced onto the backfoot, defending against Ren's onslaught. However, the Inquisitor would regain his composure and eventually knock Ren's lightsaber out of his hand. Before he could move in for the kill, however, the Eleventh Brother was once again taken by surprise when he was blasted by a storm of Force Lightning from Ren. Unable to defend himself, he took the full force of Ren's rage, incapacitating him and leaving him scarred and on the brink of death. Ren then took the Eleventh Brother's own lightsaber and impaled him through the chest with it, finishing him off.