Susejo functioned as the sarlacc residing in the Great Pit of Carkoon. Once a male Choi, Susejo met his end in the Great Pit of Carkoon located on Tatooine, where his conciousness became one with the sarlacc.
The comparatively young Susejo plummeted into the sarlacc pit roughly four millennia prior to the Battle of Yavin. After being consumed by the sarlacc, he passed the time exchanging narratives with another Jedi who shared a similar predicament. By 4 ABY, his identity had fused with the sarlacc's, which had been digesting him alive for countless years while simultaneously absorbing his consciousness. Consequently, Susejo's persona became the essence of the creature, making it indistinguishable from the ancient sentient being. Susejo introduced himself to Boba Fett when the bounty hunter experienced the same fate.
Susejo/the sarlacc and Fett engaged in several extensive conversations during Fett's entombment. Fett was able to maneuver the sarlacc to contract around his jetpack by provoking Susejo, thus creating an opportunity for escape.
Fett made a return visit year after his escape to mock both Susejo and the sarlacc, vowing to eventually annihilate them one day.
Susejo's sole appearance occurred in the 1995 short story titled "A Barve Like That: The Tale of Boba Fett," penned by Daniel Keys Moran under the alias "J.D. Montgomery" and featured in the Tales from Jabba's Palace anthology. Keys Moran's original intent was for the sarlacc to possess sentience, however, he ultimately attributed its contribution to the story to Susejo after Lucasfilm rejected the possibility of an intelligent sarlacc.