Yasto Attsmun, hailing from Listehol, was a tyrannical baron of the Ungrila male species. He helmed Attsmun Cybernetics and possessed the yacht known as the Undisputed Victor. During the era of the Cold War involving the Resistance and the First Order, he frequented the planet Cantonica, throwing nightly parties aboard his yacht as it navigated the Sea of Cantonica. On one occasion, the baron engaged in conversation with arms dealer Jerdon Bly at a yacht gathering, only for Bly to be murdered by Attsmun's masseur, Lexo Sooger. To facilitate his getaway, Sooger initiated a false alarm about a fire onboard, prompting a rapid evacuation by the baron and his guests. In the year 34 ABY, Attsmun hosted yet another party on his yacht, where he unsuccessfully pursued a romantic relationship with Ubialla Gheal, the owner of a local club. Later in that same year, Attsmun's quest for an ancient relic ultimately led to his end.
Serving as the leader of Attsmun Cybernetics, Baron Yasto Attsmun amassed considerable wealth through the sale of cybernetics and droids. His creations included the Attsmun Industries Droid, the Attsmun Industries elite Droid, and the Attsmun Industries Heavy Droid, all distinguished by their blood-red paint, his preferred hue.
Listehol's Ungrila male, Baron Yasto Attsmun, dedicated time on the planet Cantonica amidst the Cold War between the First Order and the Resistance. He was known for his constant parties held on his yacht, the Undisputed Victor, as it sailed the Sea of Cantonica, with many guests returning each night. During his time on Cantonica, he frequented Zord's Spa and Bathhouse in Canto Bight, where he was a client of Dor Namethian masseur Lexo Sooger.
During one of Attsmun's parties, he engaged in a conversation with arms dealer Jerdon Bly at the rear of the Undisputed Victor, shortly after the yacht had departed from the Canto Bight boathouse. The baron inquired about an arms deal that Bly was arranging for the following day with the First Order. Bly then requested an introduction to Lady Centada Ressad, who was also a guest on the yacht. After facilitating the introduction, Attsmun excused himself, allowing Bly and Ressad to converse privately, and proceeded to engage with another group of guests.
Soon after Bly and Attsmun concluded their discussion, Sooger was discovered disguised as a waiter in a restricted section of the yacht by one of the baron's security personnel. Sooger, under orders from Contessa Alissyndrex delga Cantonica Provincion to kill Bly, fabricated a story for the guard, claiming the baron had sent him to deliver a celebratory drink for winning a bet on a fathier race. The guard believed the fabrication and left Sooger alone, who then lured Bly to a secluded area of the Undisputed Victor and murdered him. To cover his tracks, the masseur initiated a false alarm about a fire onboard the yacht, causing the baron and all his guests to evacuate.
After the cold war escalated into open conflict between the two opposing sides in the year 34 ABY, Attsmun hosted another party on his yacht. During the festivities, he stood at the vessel's railing with Ubialla Gheal, who was the owner of a nightclub in Canto Bight. They raised their glasses in a toast, but Gheal rejected the baron's romantic advances.
Attsmun became consumed with the pursuit of eternal life, leading him to conduct experiments on sentient and non-sentient beings, driven by the belief that the combination of ancient relics and his cybernetics held the key to immortality.
At some point, Attsmun enlisted cyborg treasure hunter Lens Kamo and her Gergilla companion Ayuu to locate ancient relics. He was convinced that these relics, combined with his cybernetics, held the secret to eternal life. Eventually, Kamo discovered Attsmun's experiments, prompting her and Ayuu to attempt an escape from the baron's laboratory. During their escape, Ayuu was seemingly killed by the baron. However, it was later revealed that Attsmun had captured the gergilla and subjected him to experiments, cybernetically enhancing him with a control switch to ensure his obedience.
At some point, Attsmun learned of an ancient Sith relic and set out to find it. In 34 ABY, he captured the Dyplotid Deek in the Sardeevem Chasm on Batuu and tortured him to death in an attempt to discover its location. Later that year, Ithorian collector Dok-Ondar hired Lens Kamo and a Droid repair technician to acquire a Sith relic. While exploring the Cavern of the Moons on Batuu, the technician was confronted by two of the baron's droids, and a hologram of Attsmun appeared. Attsmun offered the technician the opportunity to join his cause.
The technician responded by destroying the two droids and escaping the Cavern of the Moons, damaging some of Attsmun's droids in the process. Following this incident, the Baron and his droids ventured to an ancient Jedi Temple, where he deployed many of them to attack the technician and Kamo. The technician managed to hold off the droids long enough for Lens to secure the relic. Attsmun attempted to persuade Lens to hand over the relic while the technician caught up with her, but she refused.
As the two attempted to flee the temple, they were cornered by Attsmun and two of his droids on a bridge. Attsmun threatened them, demanding they surrender the relic and forget the entire situation. When Kamo accused the Baron of killing her partner Ayuu, the Baron revealed that he hadn't killed Ayuu but had instead "made him better." The Gergilla then leaped onto the bridge. Attsmun commanded Ayuu to "relieve your former partner of the relic, pull her arms out - but only if you have to." Ayuu responded by charging at Kamo, shattering the stone pillars supporting the bridge and causing everyone on it to plummet into the deep chasm below.
After the fall, the technician awoke to find Ayuu emerging from the rubble. The massive gergilla spotted the technician and charged to attack. Ayuu's former partner Lens Kamo jumped onto the gergilla's back, attempting to use his control switch to free Ayuu from Attsmun's control. However, Kamo accidentally dropped the control switch onto the ground. Ayuu threw her off his back, rendering her unconscious. The technician retrieved the control switch, deactivated it, and freed Ayuu from Attsmun's control. Ayuu collapsed to the ground, unconscious. Kamo regained consciousness and rushed over to the technician, inquiring about Attsmun's whereabouts. Attsmun awoke and approached the pair, holding them at gunpoint with his blaster. Just as the baron was about to kill them, Ayuu stirred, seized the Baron, and slammed him against the cave walls, killing him. Ayuu hurled Attsmun's lifeless body onto the ground with a deafening roar. The baron's body was left in the collapsing cave as the technician, Kamo, and Ayuu escaped with the relic. Attsmun's body was likely crushed in the resulting cave-in.
Attsmun was an alien distinguished by his white hair. Known as a tyrant, he lacked generosity and consistently disregarded those he considered beneath him, never acknowledging or even looking at them. While conversing with Bly, he maintained a facade of politeness but exuded an underlying contempt.
Yasto Attsmun was conceived for the film Star Wars: Episode VIII The Last Jedi; however, prior to its release on December 15, 2017, an image of the character was initially revealed in an issue of People magazine. Subsequently, the character was featured in the short story "Hear Nothing, See Nothing, Say Nothing," penned by Rae Carson and released as part of the Journey to Star Wars: The Last Jedi promotional campaign for the film on December 5, preceding the film's release.
Creature concept designer Jake Lunt Davies created concept art of Attsmun for the film, titled "Casino Alien 11." The character was also incorporated into another concept piece by concept artist Adam Brockbank titled "Yacht Version 1." Director Rian Johnson provided Attsmun's dialogue in the film, consisting of the three words "Pablo Rayne Kiri." These words are a reference to Lucasfilm Story Group members Pablo Hidalgo, Rayne Roberts, and Kiri Hart, respectively.