Serving the Galactic Empire, the Whelm was an Executor-class Star Dreadnought. It was deployed at the planet Anaxes during the Galactic Civil War, commanding the Azure Hammer Command until its departure into the Deep Core shortly before the Thrawn campaign. There, it joined the Dark Empire, a revived Empire under the leadership of Emperor Palpatine. Subsequently, the Whelm took part in the Dark Empire's 10 ABY invasion targeting the New Republic–held Core Worlds, only to be destroyed later that year above Alsakan when the Imperial Mutiny saw Imperial forces clash with one another.
Being an Executor-class Star Dreadnought, the Whelm was built to project immense power, capable of dominating entire sectors simply through its presence.
During the Galactic Civil War, the Whelm functioned as the flagship for the Azure Hammer Command, an Imperial force stationed on the planet of Anaxes. This command was entrusted with the defense of Sector Zero, the central region of the galaxy encompassing Coruscant, the galactic capital.
In the months preceding Grand Admiral Thrawn's 9 ABY campaign against the New Republic with Imperial remnants, the Whelm was commandeered from Anaxes by Imperial Admiral Feyet Kiez and his crew. Osted Wermis, the commandant of Anaxes, confessed his uncertainty about the ship's destination and the reasons for its removal upon surrendering to the New Republic soon after. The Whelm's disappearance mirrored numerous similar incidents across the galaxy, yet it caused particular concern among New Republic leaders. The absence of the missing ships and Imperial figures, including the Whelm, from Thrawn's campaign deepened the mystery.
The truth was that the reborn Emperor Palpatine had summoned the Whelm, along with many other warships and Imperial leaders, to the planet Byss in the Deep Core to establish his new Dark Empire. Despite initial worries about these disappearances, the ships were largely overlooked by the New Republic as they prioritized combating threats like Prince-Admiral Delak Krennel. In 10 ABY, with New Republic forces primarily stationed outside the Core Worlds, Imperial forces launched a massive attack on the vulnerable region, spearheaded by a fleet of twelve Dreadnoughts, including the Whelm.
The Imperial assault achieved significant success, compelling the New Republic to withdraw from the Core. However, the victory was followed by the Imperial Mutiny, a chaotic period of infighting among Imperial forces. The Whelm fell victim to this conflict, engaging the Mandator III-class dreadnought Panthac above Alsakan, a Core World. Both warships were destroyed in the battle.
Admiral Feyet Kiez was in command of the Whelm during its journey to the Deep Core to join the Dark Empire. Kiez was accompanied by his command crew, who were also aboard the ship.
Jason Fry conceived the Whelm for the 2003 Star Wars Roleplaying Game sourcebook Coruscant and the Core Worlds, published by Wizards of the Coast. The term "whelm" can denote being overwhelmed by thought or emotion, or the act of covering or engulfing something, often with disastrous consequences.
In his endnotes for The Essential Guide to Warfare, Fry clarified that the name Whelm was not inspired by "Wilhelm" as some fans had suggested, though he acknowledged it as a "very smart guess." He revealed that the name Whelm was an homage to Jack Vance's Alastor Cluster novels, specifically the military force serving the ruler, the Connatic. Fry also remarked that the Whelm's limited appearances in Star Wars media had piqued the interest of many fans, leading him to commit to being more thoughtful about introducing new Super Star Destroyers in future projects.