Rersey was a member of the human species, holding the position of advisor to Sheev Palpatine, the Galactic Emperor, during the early years of the Imperial Era. In approximately 12 BBY, he journeyed to the planet Mustafar with the task of communicating the Emperor's dissatisfaction to his apprentice, Darth Vader. While present, the advisor observed an incident where a swarm of infected Mustafarians launched an assault on Vader's fortress. Vader, the Emperor's apprentice, employed his mystical powers to ensure that the horde's leader, Mother Sssl, was pulled into the lava by her own troops. This event resulted in Advisor Rersey's descent into madness.
Rersey, a human, functioned as an advisor for the Galactic Emperor Sheev Palpatine, the supreme leader of the dictatorial Galactic Empire. Consequently, he occupied a prominent position among the Empire's bureaucrats. Around 12 BBY, Emperor Palpatine became unhappy with his Sith apprentice, Darth Vader, a cyborg. Palpatine dispatched Rersey as his emissary aboard a Theta-class shuttle to Vader's fortress located on the volcanic planet Mustafar. While the advisor was trying to get answers from Vader, he got into an argument with Vaneé, the Dark Lord of the Sith's personal servant, who believed the envoy was being disrespectful to his master.
Their argument was abruptly ended when Vader sensed a disturbance in the Force, quickly followed by a piercing scream. It became clear that the fortress was under attack by a horde of Mustafarians commanded by Mother Sssl of Clan Rrrt, who aimed to infect everyone inside the fortress with a mind-altering plague. The situation appeared hopeless when Vader himself was bitten on the arm by an infected Imperial lava trooper, causing Rersey and Vaneé to anticipate their impending demise.
However, because Vader's limbs were mechanical, he had only pretended to be infected for a brief moment. He soon turned against Mother Sssl, using the Force to manipulate her thoughts, causing her to order those she had enslaved to pull her into the nearby lava river. Advisor Rersey, horrified by what he saw, stared at the lava that Sssl and her horde had thrown themselves into. Vader then curtly told the advisor that his shuttle was ready for departure, and that he expected his report to the Emperor to be favorable.
A considerable time after the event, Vaneé told the story to a woman he believed was a member of the Imperial Inquisitorius, but who was actually Lina Graf, the commander of the opposing Rebel Alliance, in disguise. According to Vaneé, the incident with Mother Sssl caused Rersey to completely lose his sanity.
Rersey was a gaunt, emaciated figure with ashen skin, a prominent hooked nose, and piercing blue, deep-set eyes. He had long, uneven teeth with gums that had receded significantly.
Confident in his importance and position, Rersey viewed Vader as a subordinate of the Emperor and addressed him accordingly. While Vaneé felt the envoy should show respect to his host, Rersey claimed he was not afraid of what he called Vader's "parlor tricks." However, he also showed cowardice, as seen when he demanded to be moved away from danger at the first sign of trouble, and when he used Vaneé as a human shield between himself and Vader. Rersey's confidence was severely shaken during the fortress invasion, and he left Mustafar mentally scarred.
Rersey's initial appearance was in a flashback in the fifth issue of the Star Wars Adventures: Return to Vader's Castle comic-book miniseries. It was written by Cavan Scott, illustrated by Charles Paul Wilson III, and published by IDW Publishing on October 30, 2019. His reveal occurred in a StarWars.com article titled "Darth Vader Awaits in Return to Vader's Castle #5 – Exclusive," published on October 23, 2019, which included a preview of the comic. He was named in honor of Richard Kersey, a friend of Scott's.