In 137 ABY, Darth Krayt's chief lieutenant and Sith Lord, Darth Wyyrlok III, of the One Sith Order, embarked on a mission to Prakith. Krayt, Wyyrlok's Master, needed to eliminate the Yuuzhan Vong implants that were killing him, which necessitated this mission. Wyyrlok, after extensive research into ancient Sith secrets, consulted a Sith holocron in his possession. That holocron belonged to Darth Andeddu, a long-dead Dark Lord who was known for preserving his essence after death. Wyyrlok then journeyed to Prakith, Andeddu's homeworld in the Deep Core, to gather information to aid Krayt.
Wyyrlok located Andeddu's Keep, where he encountered the Malevolence, a previously unknown Sith cult that worshipped Andeddu and barred Wyyrlok from entering further. Wyyrlok, undeterred, eliminated all the cultists except for Gerlun, who then sacrificed his own life to revive Andeddu's corpse. Andeddu and Wyyrlok engaged in a Force abilities duel, which Andeddu ultimately lost. After the second death of the ancient Sith Lord, Wyyrlok returned Andeddu's body to its sarcophagus and sealed it.
Wyyrlok's mission was only partially successful, since he could not find any information in Andeddu's vast collection of Sith knowledge that would help him keep Krayt alive. However, he did realize that the Dark Lord was actually being killed by his own doubts about surviving to see his dream of a stable galaxy under Sith control come true.
A'Sharad Hett, who would later become Darth Krayt, the Dark Lord of the Sith, had been captured by the extra-galactic Yuuzhan Vong species and implanted with their Yorik-Kul slave seeds decades before the conclusion of the Sith–Imperial War and the start of the Second Imperial Civil War. Hett was gradually losing his fight against the seeds, despite being able to fight their effects with his growing strength in the dark side of the Force. He had taken on the role of Dark Lord and renamed himself the Dragon of the Sith by 137 ABY, but the coral seeds still posed a threat of turning him into a mindless shell of a man.
Krayt was able to support himself for years with healing trances and long periods of stasis, and he was cared for by his most reliable servants, the most recent of whom was Darth Wyyrlok the third. Wyyrlok, despite being the most knowledgeable member of Krayt's Order in Sith lore and ritual, was unable to discover a method to treat his Master's affliction. As a result, he turned to a holocron that belonged to Darth Andeddu, an ancient Sith Lord who was known to have revived his flesh following his own death. The gatekeeper of Andeddu's holocron refused to reveal its secrets in order to save Krayt, whom it deemed an imposter to the Sith legacy. The gatekeeper only revealed the location of Andeddu's Keep on his homeworld of Prakith after Wyyrlok hinted at actually resurrecting Andeddu's body. Wyyrlok immediately departed in his personal fighter for the Deep Core in search of Andeddu's domain and his highly sought-after life-sustaining powers.
Wyyrlok arrived on Prakith with Andeddu's holocron and entered Darth Andeddu's crumbling fortress, where he was quickly met by members of the Malevolence cult, who were guarding Andeddu's tomb. They refused to let Wyyrlok pass and approached him with lit lightsabers, intending to kill him. Wyyrlok, however, demonstrated his mastery of Sith sorcery by employing illusions to trick the cultists into killing one another. Gerlun was the only survivor, and he swore allegiance to Wyyrlok and led him to Andeddu's tomb. Wyyrlok was told by the gatekeeper to put the holocron on Andeddu's body in order to revive him and learn all of his secrets with Andeddu's holocron in hand. Wyyrlok declined, preferring to simply learn what he could from Andeddu's extensive collection of books and scrolls. Gerlun, in an attempt to get revenge on Wyyrlok for defeating his fellow cultists, used the Force to grab the holocron and place it on Andeddu's body, and to their surprise, the holocron's power was depleted as Gerlun's own life force was used to restore Andeddu's life.
Even though Andeddu had been revived, he refused to share his knowledge with Wyyrlok, claiming that true Sith did not share power. He then assaulted Wyyrlok with a barrage of Sith lightning, but Wyyrlok absorbed it in his palm. Andeddu challenged Wyyrlok to a duel of Force abilities, immediately using the Force to push him away while creating illusions of massive rocks, which he then hurled at Wyyrlok.
Wyyrlok was not easily defeated, and he quickly saw through Andeddu's ruses. He realized Andeddu was afraid of dying, so he took control of Andeddu's lava and flame illusions to seemingly destroy all of Andeddu's books and scrolls. Andeddu was horrified by the destruction of his priceless artifacts and believed Wyyrlok's illusion to be real, even as Wyyrlok turned the lava and flames against him. Andeddu perished a second time, consumed by his own fear of death.
Wyyrlok placed Andeddu's soulless body back in its tomb and began studying much of the lore in Andeddu's collection. Wyyrlok, however, discovered nothing in Andeddu's Keep that discussed how to heal or preserve life through the dark side of the Force. Wyyrlok realized that Darth Krayt was being killed by more than just physical ailment; his doubts about living long enough to ensure stability in the galaxy were having just as much of an impact on him as the Vong slave seeds. Wyyrlok took several books and scrolls, left the keep, and went back to his Master, even more determined to find another way to heal him.
Krayt eventually discovered a way to get rid of the seeds for good, but he was unable to fully utilize the power. Krayt was lured into a trap by the Jedi and Imperial Knights of the Fel Empire sometime after Wyyrlok's mission to Prakith, where he briefly subjected himself to the healing abilities of the ancient Sith spirit of Karness Muur, who was using one of the Jedi as a host body. Krayt was fatally wounded by one of the Imperials when the trap was sprung, shortly after figuring out how Muur was killing the slave seeds. Krayt asked Wyyrlok to place him in a bacta tank when Wyyrlok discovered him alive so that his current wounds could be treated while he gained the strength to finish the purging process that Muur had started. Wyyrlok instead carried out one of the Sith's core tenets and betrayed his Master by killing him.
The Prakith mission first appeared in Into the Core, the twenty-seventh issue of the Star Wars: Legacy comic series, which was written by John Ostrander. Ostrander uses this mission to further develop Darth Andeddu's backstory by introducing both his homeworld and the Malevolence cult. Ostrander reveals here that Darth Krayt's failing condition is caused not only by the Yuuzhan Vong implants, but also by his anxieties and fears.