Sentinel (Contingency)

The sentinels exhibited a humanoid form, with a physical structure closely resembling the B1-series battle droids previously employed by the Trade Federation and the Confederacy of Independent Systems. However, in contrast to those battle droids, sentinels were clothed in vibrant red robes, reminiscent of those worn by the Emperor's Royal Guard. Some of these droids wore red jackets over their robes, featuring integrated gloves, while others lacked such hand coverings.

In further distinction from battle droids, sentinels possessed heads designed as helmets with a sleek glass dome. These glass masks functioned as screens, displaying realistic images of Palpatine's face after his passing. Additionally, sentinels had human-like five-fingered hands equipped with a central holoprojector in their palms, along with a retractable needle used to authenticate the recipient of a message through blood analysis.

The creation of the sentinels was part of the Contingency plan. Their primary function was as messengers: they would appear, confirm the recipient's identity, deliver commands, and then depart. However, those designated for Gallius Rax possessed greater autonomy, approaching actual sentience. They also demonstrated the ability to pilot starships and defend secret assets by eliminating intruders. The Hall of Imperial Register served as the data source for the sentinels executing Operation: Cinder, utilizing its stored information and a complex set of algorithms to identify suitable candidates for carrying out the destruction.

The sentinels also had a unique design, with a core programming to express a specific emotion, which The Surgeon speculated to be loathing or spite. They also had access to many mathematical formulas that measured an individual's loyalty (from the Emperor himself to the broader Empire), resourcefulness, and conscience. The formulas recognized variables such as past kills (during or outside of military service), disciplinary actions, family trauma, education, genetic predisposition, species predispositions, personal associations, history of obedience to unlawful commands, involvement (including nonparticipatory exposure) in physical interrogation, and MDC-count. The coding in a sentinel was ultimately designed to assess individuals as parts of units, and then render judgement on the units as a whole, determining the moral character of a battalion or fighter wing based on current or past leadership and membership. These calculations gave the most weight to a unit's worst members, tracing their corrupting influence on those around them. Fundamentally, the sentinels were deployed to locate units most susceptible to corruption and subsequently exploit that corruption.

The initial production of sentinels occurred in or before 20 BBY, during Palpatine's tenure as Supreme Chancellor of the Galactic Republic amidst the widespread galactic Clone Wars against the Confederacy of Independent Systems. During this period, many were assigned to protect the newly constructed Observatory on Jakku, one of many similar buildings located throughout the galaxy. These sentinels guarded the Observatory and the various ancient Sith artifacts housed within. The sentinels were critical in transmitting the Emperor's Contingency plan, which involved destroying the Empire upon his death and sending select worthy Imperials into the Unknown Regions to rebuild the Empire.

In the days following the Emperor's demise at the Battle of Endor, a sentinel traveled aboard a Lambda-class T-4a shuttle to the Star Destroyer Torment, captained by Lerr Duvat, at Rendezvous Point: Victim in the Outer Rim. The sentinel encountered Duvat on the ship's bridge, after Duvat dismissed his officers. After confirming Duvat's identity using blood, the sentinel delivered a posthumous message from Emperor Palpatine, declaring the immediate commencement of Operation: Cinder. The sentinel then designated Duvat's target: the Mid Rim world of Naboo. Another sentinel was sent to Fleet Admiral Gallius Rax, charged with executing the Contingency.

Another sentinel droid was dispatched to Admiral Garrick Versio and met him on the bridge of his Star Destroyer, the Eviscerator, above the admiral's homeworld of Vardos. Versio chose to share the Messenger's presence with his daughter, Iden Versio, commander and leader of the elite Inferno Squad. The droid delivered the first part of the message, to commence Operation: Cinder, to the pair; when Iden asked about the target the droid suddenly lunged aggressively at her declaring that she was not a verified recipient, startling both Versios. Unknown to Iden, the target was in fact their own homeworld of Vardos, though Garrick did not share this information with his daughter.

One of the Messengers arrived in the hands of the 204th Imperial Fighter Wing, and it ordered them to commence Operation: Cinder. It then ceased to provide updates. After weeks, it served as a centerpiece of a shrine aboard the Aerie to what the Imperials had lost. After the Aerie was stripped of parts and served as a decoy during the Troithe operation, the Messenger survived the ship's destruction and was found by the wreckage of the Edict. It later had the misfortune of wandering upon Yrica Quell when she was in the midst of sending a signal to the New Republic, resulting it in being fatally shot and deactivated. It was then dismantled by both her and her commanding officer, Soran Keize before it's core parts were brought to a droid known as The Surgeon. It dissected the Messenger and gave crucial intelligence to Yrica Quell, who shortly afterward, shared the information with the New Republic and Soran Keize.

In 5 ABY, three months after Endor, the Rebel heroes Luke Skywalker and Shara Bey discovered a manufacturing line of sentinels while carrying out a mission to retrieve fragments of a Force-sensitive tree from an Imperial base on Vetine. The assembly line was destroyed during the confrontation between the Rebels and Commandant Hurron's troops.

Leading up to the Battle of Jakku, a sentinel informed the now-Counselor to the Empire Rax that the deposed Grand Admiral Rae Sloane was approaching the Jakku Observatory with Niima the Hutt's caravan. During the Battle of Jakku, Rax traveled with the former Commandant Brendol Hux, his son Armitage, his child soldiers, and Adviser Yupe Tashu to the Observatory on a transport piloted by the sentinel. Using the sentinel pilot, Rax transmitted commands ordering the turbolasers and sentinel droid defenses to power down.

The sentinel pilot later piloted a replica of the Emperor's yacht Imperialis into the Unknown Regions. The ship's passengers included both the Huxes, the child soldiers, and Grand Admiral Sloane. During the journey, the sentinel told Sloane that a dozen path coordinates had been transmitted to Imperials considered loyal to the late Emperor. The droid informed her that all sentinels and messengers were programmed to serve his will even in death. After several months of traveling, the Imperialis rendezvoused with the Emperor's flagship Eclipse.

Years later, the B1 battle droid R0-GR wrote the droid guide "droidography." In the section describing the increasingly blurred line between organics and droids, he recounted that it was rumored Palpatine used sentinel droids bearing his image to deliver direct messages to officers. R0-GR felt this made the Emperor even more horrifying and included an image of a sentinel droid.

The initial appearance of sentinel droids occurred in Shattered Empire 2, the second installment of the Marvel Comics miniseries Star Wars: Shattered Empire, which was released on October 7, 2015. Greg Rucka conceived the concept, while Marco Checchetto provided the droid designs.