One item of note recovered from base Talon include what appears to be a heavily modified dark trooper exosuit, referred to as an 'Onyx trooper'. This item includes a large arsenal, which can only be described as 'overkill'.
—Excerpt from a New Republic report following the capture of Base Talon
Onyx troopers were what several secret Imperial prototypes developed at Base Talon were called. They were essentially modified dark troopers, and were the brainchild of a scientist at the facility who felt that the cancellation of the Dark trooper project was unfair, and taken it upon himself to give it another chance. As a result, he developed a new form of exoskeleton based on the original dark trooper, feeling that a droid version would be too expensive and stupid. The name of these new form of weaponry came from the fact that all of the prototypes were spray-painted dark black; the proper name of the project was DKR-12, but eventually the name 'onyx trooper' stuck, and the project was renamed Project Onyx.
The main characteristics of these 'onyx troopers' included inbuilt shields that were even stronger than that of old droidekas, heavy plasma weaporny, missile launchers, seismic generators, density projectors, and shrapnel launchers. They were also larger and more streamlined than their dark trooper predecessors. The final versions of these exosuits were to be moderately expensive, as this equipment was deliberately made low-quality. Only one proper version of the onyx trooper exosuit was ever made, and it was never used in combat.
The prototypes of the onyx troopers were used when Base Talon came under attack by the rebel alliance shortly after the battle of Endor, where they were unleashed upon the rebel forces, despite being unfinished. They dealt much damage, but were eventually destroyed by concentrated fire. The onyx trooper project came to an end upon the base's capture.