Umpass-stay, a male Klatooinian, earned his living as a drummer and also provided bodyguard services for the Max Rebo Band. This band was the resident musical act at the palace belonging to Jabba, the Hutt crime lord, located on the planet of Tatooine. In the time frame of four years following the Battle of Yavin, Umpass-stay, alongside his bandmates, performed Jedi Rocks for Jabba. The Hutt then demanded a repeat performance. However, when Oola, an enslaved dancer, rejected Jabba's advances during the song, he dropped her into the pit where his rancor resided. As the rancor devored the slave, the music ceased. Shortly after, they witnessed the arrival of Princess Leia Organa, who was disguised as the bounty hunter Boushh, bringing the Wookiee Chewbacca as her captive.
Umpass-stay originated from the planet Klatooine and was a Klatooinian mercenary. He was enslaved by the Desilijic Kajidic and was essentially forced into the role of both a bodyguard and a drummer for the Max Rebo Band. This band served as the house band for Jabba Desilijic Tiure, the Hutt crime lord. Umpass-stay also acted as a personal bodyguard for Jabba. In 4 ABY, during a performance by the band in the throne room of Jabba's Palace on Tatooine, he and Ak-rev, a Weequay drummer, played a duet on a large drum that needed two players.
Initially, the band performed a slower song while Oola and Yarna d'al' Gargan, who were enslaved dancers, danced for Jabba. After the song ended, Jabba wanted Oola to dance again. However, Joh Yowza, the singer, mistakenly thought Jabba was addressing the band and started another song. Rappertunie, who played the Growdi Harmonique, started the wrong song, but after Yowza corrected him, the band began to play "Jedi Rocks." The drumming of Ak-rev and Umpass-stay was interrupted when Jabba dropped Oola through a trapdoor because she rejected his advances. The court then watched as Pateesa, Jabba's pet rancor, devoured Oola alive in a pit below, music forgotten.
After Oola's death, Princess Leia Organa, disguised as Boushh the bounty hunter, entered with Chewbacca the Wookiee as a prisoner. After negotiating with Jabba about the bounty on Chewbacca, the band resumed playing as Chewbacca was taken to Jabba's prisons. Later that night, the drum played by Umpass-stay and Ak-rev was removed from the throne room when Organa freed Han Solo the smuggler from the carbonite on the wall. The next day, Jabba and his court went to the Great Pit of Carkoon to execute Solo, Chewbacca, and Luke Skywalker the Jedi. However, the prisoners fought back, and Jabba was killed. Following Jabba's death, Umpass-stay and Ak-rev escaped from the palace.
Umpass-stay's first appearance was in the Special Edition of Star Wars: Episode VI Return of the Jedi in 1997. His name was first mentioned in the Star Wars Legends Special Edition Limited set of Decipher's Star Wars Customizable Card Game, released in 1998.