The Decraniated were a type of servant created by the renegade surgeon Cornelius Evazan, initially for Dryden Vos. Several of these servants were present on Vos's ship, the First Light. When the Partisans launched an assault on an Imperial convoy in Jedha City, members of the Decraniated were also observed there, prior to the city's destruction by the Death Star.
Cornelius Evazan originally conceived of the Decraniated as a profitable venture for his then-superior, Dryden Vos. These beings were engineered to be as obedient as droids. Evazan utilized cybernetic technology to rob his victims of their identities, transforming them. He then sold them as servants, against their will, using catalogs. On Jedha, Evazan exploited the ongoing insurgency strikes to kidnap casualties and convert them into Decraniated.
By 10 BBY, Doctor Cornelius Evazan began his Decraniated project while in the service of Dryden Vos, who was second-in-command of Crimson Dawn. Evazan envisioned it as a way to generate income for his boss. Some of these Decraniated became servants aboard Vos's personal yacht, the First Light. Chelli Aphra once encountered them in a catalog.
Later, while on Jedha, Evazan assembled Caysin Bog, a casualty of an insurgency attack, as an early Decraniated prototype. Evazan used cybernetic technology to alter injured victims of the local insurgency, stripping them of their identities before forcing them into servitude. Two Decraniated members were briefly spotted in a Jedha City café, near a group of Imperial officers, just as the Partisans attacked an Imperial convoy. This occurred before the city was destroyed by a single-reactor superlaser blast from the newly operational Death Star.
Even after Evazan departed and Jedha City was destroyed, some Decraniated remained on Jedha. They aided the surviving Partisans during their campaign to disrupt the Imperial mining operations in the area.
The concept of a character with cybernetic augmentations similar to the Decraniated initially appeared in concept art for the bar in Takodana Castle. This art was created by Glyn Dillon during the pre-production phase of Star Wars: Episode VII The Force Awakens in November 2013, but the idea was ultimately not implemented in the film.