Savathûn's Worm

Savathûn's Worm is a Worm larva that once resided within the body of Savathûn, the Witch Queen and provided her with paracausal abilities, as is the case with all Hive. After being exorcised from the Witch Queen by Mara Sov and her Techeuns, the parasite was kept alive by the Awoken Queen, to whom it grudgingly provided assistance in return for its continued survival. It is currently being kept within the Exotic Grenade Launcher Parasite.

Biography
After meeting the Worm Gods in the depths of Fundament, Savathûn (then known as Sathona) voluntarily allowed herself to be implanted with a Worm larva, as did her sisters Aurash and Xi Ro. The Worm granted her biological immortality and paracausal abilities, allowing her to become powerful through the Sword Logic. It remained within her body for billions of years, until it was removed by Mara Sov and her Techeuns, who managed to keep it alive without a host. Mara promised the worm that it would be given a new host in due time; the Worm was led to believe this new host would be Mara herself.

Ultimately, Savathûn's Worm would find itself outmaneuvered by Mara Sov after she offered it a new host in exchange for it's knowledge of Savathûn's role during Humanity's Collapse. When it appeared in a ritual that Mara was about to become it's new host, she instead transformed it into a weapon called Parasite, much to it's shock and dismay. The Awoken Queen clarified that it's new form will allow it to continue living but it's new "host" is now effectively a prison. The Guardian would use the weapon Savathûn's Worm had become to fight off the Scorn as Mara Sov finished the ritual. Despite being angry at being deceived, Savathûn's Worm nonetheless held up its end of the bargain, telling Mara and the Guardian that as the Witch Queen observed the Collapse on behalf of the Witness, she instead tricked the Witness when it turned a violent gaze towards the Traveler, which ultimately turned the tides and forced the Witness back into the stars. With that, Savathûn's Worm refused to speak of it anymore, but Mara Sov was satisfied with the information, tasking the Guardian to keep the weapon holding the worm close.

Following the Guardians epic struggle against Rhulk, Disciple of the Witness, Mara Sov called upon them to prevent the Scorn from claiming the Disciple's ruptured Sunken Pyramid for themselves. With Savathûn's Worm present, it recognized the Pyramid as the home to "Worm Father" and "Worm Mother", stating it was good to be back. It even asked the Guardian for a chance to visit the worm mother, which an annoyed Ghost interpreted as a "family reunion". Reluctantly, the Guardian fulfilled it's request by taking it to an overlook that allowed it to see the carcass of the Worm God, Xita, the Nurturing Worm. There, Savathûn's Worm states that even though the Worm Mother's sleeps eternal, her role persists and it will carry her legacy the best it can.

Trivia

 * The manner in which Savathûn's Worm speaks is similar as to how Variks speaks, possibly due to them being voiced by the same voice actor.
 * If one has the Parasite exotic grenade launcher equipped while running the Birthplace of the Vile strike in Savathûn's Throne World, the worm will speak to the Guardian, generally to taunt them.

List of appearances

 * Destiny 2: Season of the Chosen
 * Season of the Splicer
 * Season of the Lost
 * The Witch Queen