Caysin Bog was a male humanoid individual hailing from Teres Lutha Minor, a world characterized by high-gravity. During an insurgency attack on the moon of Jedha, Bog was torn to pieces. A surgeon who went by the name "Roofoo," actually Cornelius Evazan, then performed surgery to reassemble him. In 1 BBY, Bog was present in Jedha City and bore witness to an attack launched by the Partisans against an Imperial patrol, an event that took place shortly before the city's destruction at the hands of the Galactic Empire's Death Star superweapon.
Bog successfully evaded death caused by the Death Star, and in the aftermath of the Battle of Yavin, he found employment as a mercenary alongside his romantic partner, Tam Posla. Around 1 ABY, the duo accepted a contract from the Son-tuul Pride crime organization, tasking them with traveling to the planet Skako Minor under the leadership of Doctor Chelli Aphra. Upon arrival, the Skakoan Hallio Bas led the mercenary group into an Imperial ambush; however, Aphra managed to eliminate both Bas and the Imperials using an exploding tooka.
Subsequently, the group proceeded into the lab, where they encountered another Imperial force commanded by Magna Tolvan, triggering the awakening of a chthonic worm god, which proceeded to attack Bog and his companions. Dek-Nil, the mercenary droideka, ultimately eliminated the creature by causing the lab's roof to collapse. Following this, Bog and the others plundered the lab and returned to their shuttle.
After discovering the memories they were searching for were stored in Hivebase-1, Aphra led the mercenaries to the rebel flight school. They attempted to persuade General Hera Syndulla regarding their "plan", but she imprisoned them. Despite managing to escape, Bog and the others remained in their cells to gain Syndulla's trust, leading her to be willing to consider their plan. However, Bog then deployed a collection of pistols from a compartment in his neck, enabling the mercenary Sister Six to incapacitate the rebels. Against Posla's objections, they then kidnapped Syndulla.
En route to Hivebase-1, Aphra repaired Bog's diagnostics and simultaneously implanted a contingency order into him, intending to prompt Posla into fighting for them. Arriving at Hivebase-1, they feigned trading Syndulla with the resident Imperials. Aphra, however, attracted the flight school to distract the defenses, allowing them to infiltrate the complex undetected. While their presence initially went unnoticed, it was revealed during an inspection of frozen prototypes, which subsequently thawed. Aphra activated Bog's contingency order, causing him to run into the line of fire, enabling Posla to attack the prototypes. Bog perished in the process.
A humanoid male from the high-[gravity](/article/gravity] planet [Teres Lutha Minor](/article/teres_lutha_minor], Caysin Bog was ripped apart during a raid on the moon Jedha by the Partisans of Saw Gerrera. The surgeon Cornelius Evazan, using the alias "Roofoo," saved him by piecing him back together using similar techniques to those used to create the subservient Decraniated cyborgs. Bog himself noted that he served as a prototype for the Decraniated.
In 1 BBY, Bog was in Jedha City, standing near Gesh's Tapcafe, making way for an Imperial patrol, including a TX-225A Occupier tank. As he waited, the Partisans ambushed the Imperials, throwing explosives and causing civilians to scatter. Bog then met Tam Posla, a former Milvayne Authority officer hunting Evazan. They missed the surgeon by seconds and had to evacuate with Imperial forces from the city shortly after, as the Galactic Empire destroyed it with the Death Star superweapon.
Bog escaped Jedha City before its destruction. After the Rebel Alliance destroyed the Death Star at the Battle of Yavin, he worked as a mercenary with Posla, his romantic partner. Posla used his mercenary pay to fund his hunt for Evazan.
Around 1 ABY, they were amongst mercenaries hired to travel to Skako Minor for the Son-tuul Pride criminal syndicate on Son-tuul. The group waited for Doctor Chelli Aphra in a patrol transport near a settlement on Son-Tuul. In the vehicle, Bog and Posla held hands while Posla listened to music. Aphra scanned her new crew, noting Bog's history with Evazan and his relationship with Posla.
Before leaving for Skako Minor, Aphra had to leave one team member behind, as they were too heavy for the ship. As Imperials surrounded the transport, Aphra ordered Viscount Rabael Dir Glorio to stop them. Aphra piloted the ship with Bog and the others, leaving Glorio behind.
On Skako Minor, they followed their Skakoan guide Hallio Bas, believing he would lead them to the workshop of Wat Tambor. Instead, Bas led them to Imperial stormtroopers with whom he had a deal. Before the Imperials could execute Bog and his comrades, Aphra begged them to spare her pet, the genetically spliced tooka clone Flufto. Bas took the pet to eat later, after which Aphra said a code phrase causing the tooka to explode, killing the Imperials and Bas.
Bog and the team survived the explosion. A fleeing stormtrooper was ordered to be stopped by the cyborg mercenary Rexa Go, but Bog and Posla refused, reasoning that the alarms were already triggered and there was no need to kill someone who had broken no law. The Defel Glahst Ombra killed the trooper instead, after which the team moved inside Tambor's lab.
Inside, Bog noticed a sparkling techno-totem and reached for it, but Aphra stopped him, suspecting a trap. Moments later, an Imperial Delta-class T-3c shuttle crashed through the wall and landed on the totem. Stormtroopers led by Magna Tolvan emerged and opened fire, forcing Bog and the others to take cover.
The shuttle's disturbance awakened a Chthonic worm god, which erupted from the floor and attacked Imperials and mercenaries. Bog and Posla retreated, where Aphra ordered Bog to harm the god with his bayonet, as it was targeting weaponry. Posla advised Bog to ignore the order, as their contract only covered entering and holding the facility.
Aphra threw another explosive tooka at the creature, but it trapped herself and Tolvan in a part of the lab where the god couldn't reach. The creature incapacitated Bog, leaving him draped across a wall. When Sister Six pointed it out to Posla, Posla became enraged and launched missiles at the beast. The attack stopped when Bog revealed he was only slightly winded.
The pair reunited, holding each other for comfort. The droideka Dek-Nil then fired a shot into the roof, causing it to collapse and kill the god and remaining stormtroopers. Aphra ordered the team to loot, stopping briefly when they heard Aphra shoot Go to save Tolvan. Bog and the others returned to their shuttle with the loot. Onboard, Aphra informed them they had a near-suicidal mission: attacking the Imperial archive Hivebase-1, the R&D headquarters for the Tarkin Initiative.
Aphra planned to get into Hivebase-1 by offering something valuable to the Imperial officers. So Aphra, Bog and the others went to the rebel flight school, a re-purposed Lucrehulk-class battleship that trained Rebel pilots. They found the ship thanks to the files from the facility on Skako Minor. When they got there Glahst slipped away and a Alliance officer greeted them thinking they were new recruits. But when General Hera Syndulla arrived, Posla made it clear they weren't signing up and told Syndulla they had a proposal. Realizing they were mercenaries, Syndulla had them arrested and put into cells. Whilst they were in their cells, Glahst returned and jumped into Dek and Aphra's cell. Aphra was relieved at first but quickly discovered it was Magna Tolvan. Tolvan had skinned the poor Defel and used her skin as a disguise. Tolvan drew her gun but didn't realize that Dek was aware of her. Dek stunned Tolvan and she shot once reflexively with her blaster disabling the shields keeping them in the cell.
The alarms went off but the mercenaries did not flee as it would anger the rebels more. Syndulla noticed this and offered to let them leave. Aphra was still on for their proposal so Syndulla let them speak. Aphra explained that they knew how to get into Hivebase-1 and that they needed Syndulla's help. Syndulla was curious to know their plan but as Posla was about to explain, Bog opened his compartment and shot out several blasters. Sister Six caught them and started stunning the rebels. In a matter of seconds all the rebels in the room, including Syndulla, were unconscious. Posla had not been told of this plan and was furious, despite Bog's attempts explain why they didn't tell him. They almost left Posla behind as they escaped with Syndulla.
Once they were away from the flight school, Aphra contacted one of the Imperial officers in Hivebase-1 offering a trade with Syndulla. The officer accepted the offer and the crew began travelling to Hivebase-1. In the meantime, Bog let Aphra fix some of his diagnostics which had been affected during their mission to Skako Minor. What Bog didn't know was that Aphra had programmed a contingency plan into Bog in case of an emergency which could be activated from the former head set of Rexa Go. The crew jumped into range of Hivebase-1, where they were soon followed by the rebel flight school. Aphra had planned to lure the Lucrehulk-class battleship there using the tracking device on Syndulla's General plaque. The flight school found itself under attack by acidic creatures which began to breach it's hull. During the chaos of it's arrival, Aphra's team flew into Hivebase-1.
Now inside Hivebase-1, the group investigated the collection of rejected prototypes and plans which were frozen to keep under control. During their search, Magna Tolvan got onto the bridge of the flight school and took out the captain and bridge crew. Tolvan then contacted Hivebase-1 command and notified them of the presence of Aphra's crew. Aphra and her crew realized this and the frozen prototypes started to defrost around them. Before they could react, Dek was gunned down and they were pinned behind crates.
Aphra asked Posla to fend off the cyborgs with his built in weapons, but the man refused, excusing the prototypes as victims of experimentation. That was when Aphra activated the contingency in Bog's system and Bog walked into the firing line of the cyborgs, killing him instantly. Posla watched his soulmate fall to the ground and, in a fit of rage, advanced to fire upon the wave of forgotten designs.
Aphra, Syndulla, and Sister Six escaped while Posla fought the prototypes. Although Posla was heavily outnumbered, his weapons proved a match for the prototypes, and he returned to the others, traumatized from seeing Bog's death. In the following skirmish that ensued, between the mercenaries and Commander Yewl and his troops, Posla remained mourning Bog's death. Fortunately for them, Aphra used a bug planted in flight school to have it latch onto Hivebase-1 and use its X-wings to rip the datacore, in which the mercenaries were situated, out. With the datacore separated, Aphra had the complex destroyed using the now released explosive Tookas. After returning to the flight school with Syndulla, Aphra double-crossed Posla to extract Tolvan.
Following Aphra's betrayal, Posla suspected her of orchestrating Bog's death and promised to cut out her heart slowly. But until then he only focused on continuing the hunt for Evazan, which him and Bog had been up to for some time. After being traded a "fake" Evazan, Posla wished that Bog was there to see his success.
Bog had fair skin where he wasn't cybernetic. He was in a same-sex relationship with Tam Posla, warning Aphra not to disturb him while he listened to "his happy tunes". On Skako Minor, Bog told Posla about Aphra's criminal history.
Bog and Posla became bounty hunters to fund their mission to take down Dr. Cornelius Evazan, who turned Bog into a cyborg. Bog refused to kill a fleeing stormtrooper despite orders from Rexa Go, since he was not being paid per kill and the Imperial had broken no law. He and Posla refused to fight the chthonic worm god as it wasn't in their contract. When Sister Six called them crazy, Bog said knowing what mattered was more important than sanity.
After his cybernetic reconstruction, Bog had orange and white cybernetics around his neck instead of a head. His legs and lower abdomen were also cybernetic, exposing some of his guts. Bog carried a blaster on Jedha, and a bayonet on Skako Minor.
Caysin Bog debuted in Rogue One: A Star Wars Story, in the first teaser trailer released on April 7, 2016. The trailer scene wasn't in the final film, but he can be seen during the Jedha City ambush. He wasn't named in the film but was identified in Star Wars: Rogue One: The Ultimate Visual Guide by Pablo Hidalgo, released on December 16, 2016.