Osiris

"If I don't stop the Vex, there won't be anything to come back to."

- Osiris

Osiris is an old Warlock and a former Vanguard who was exiled from the City. He now scouts the Infinite Forest as a vigilante, protecting the Solar System from any signs of the Vex.

Early history
A veteran of Six Fronts, Osiris was a well respected warrior whose prowess at that battle convinced Saint-14 to recommend him to the Speaker as Vanguard Commander. He had also served as the Speaker's apprentice for a time. However, his desire for truth about the purpose of Guardians and the nature of Darkness drove him to madness. His theories were not only considered borderline blasphemous, but he was also diverting Guardians and resources away from protecting the City and refugees, and towards chasing legends and rumors, such as the Vault of Glass; it's implied that he was the one who inspired Kabr, the Legionless into going into the Vault. He studied the Hive, in particular prophesying the coming of Oryx, and is also rumored to have come "too close to understanding the Vex".

His obsession with the nature of the Darkness and misuse of resources eventually drove the Speaker to exile him, as the Speaker believed he had become as obsessed with the Vex as Toland, the Shattered had with the Hive. He is described as having a cult of personality, and has a number of disciples, such as Brother Vance, who attempt to see how far the Light can be bent before it can be broken. Osiris himself seems to have vanished, even from those who follow him, some claiming that he is at once "alive and dead."

Destiny
Whether before or after his banishment, Osiris held council with the other two powers of the Solar System, the Queen of the Reef and The Nine. His arrangements with the Queen extend to his followers, explaining their presence in the Vestian Outpost. He also receives reports from Eris Morn and has employed the Sunbreakers to work for him.

The Disciples of Osiris held a Crucible tournament in his honor called the Trials of Osiris, where they sought to recruit the toughest Guardians to their cause.

Destiny 2
In Destiny 2 in the Adventure Deep Conversation, Osiris makes contact with Ghost through the Vex network to send his regards.

Curse of Osiris
Osiris finally appears in-person and serve as a central figure in the DLC, Destiny 2: Curse of Osiris. Having returned after years of exile, Osiris makes contact with his former student, Ikora Rey, informing her that the Vex from both past and future timelines are amassing on Mercury. Though distrustful of her former teacher, knowing his dangerous ideas nearly destroyed the Vanguard, she sends the Guardian to find him and determine whether he will be a powerful ally against the Vex or a dangerous enemy.

It is also revealed that during his exile researching the Vex Infinite Forest, he created Reflections of himself that communicated with him and each other on Vex activities through time. Osiris' main goal is to destroy the Vex Mind directing their efforts in the Solar System, Panoptes, Infinite Mind but despite his efforts, all he could do was slow its progress.

During a mission through the Vex timeline, Osiris learns of the Traveler's awakening and sees a future where the Vex succeed in their plans in dominating reality which horrifies the exile. Before he can explain to his Ghost Sagira, the Vex discover their presence and attack them. Cornered, Osiris sends his Ghost through the Infinite Gate to save her and find help, despite her protests. Sagira gets damaged during the forced escaped and Osiris goes into hiding as the Vex close in.

Sagira manages to return with help in the form of The Guardian and with the aid of Ikora, they travel through the Infinite Forest to search for the exile but only find his Reflections. The Reflections guide the Guardian as they learn of the Vex's plans, showing them of the Simulant Future where the Vex have won, and of how to locate Panoptes' lair in order to destroy the Mind. However, as they succeeded in learning the location of Panoptes' lair, Infinity's Crown, Sagira gets captured by the Infinite Mind.

During the Guardian's battle with Panoptes itself, they were unable to damage the Mind and as they are about to be deleted, Osiris and his many Reflections come to their aid, stopping the deletion from completing. With little time, Osiris provides Arc charges to the Guardian to disrupt Panoptes into revealing its "eye", its only known weakness. Together, they succeed in destroying the Infinite Mind forever and free Sagira, thereby preventing the dark future from ever occurring. Departing Infinity's Crown back to Mercury, Osiris is reunited with his former student, Ikora Rey. Their reunion is pleasant and they return to being friends as he is proud of her. He politely turns down her offer to return to the City as he states there are other Vex plots to prevent but before leaving, Osiris tells the Guardians that in all of his predictions, they were the one thing he did not foresee and because of them, they all now have a future. He then travels through the Infinite Gate once more to combat the Vex but tells Ikora that the path to the Infinite Forest remains open should she or the Guardians ever need him or would like to talk, to which Ikora kindly agrees.

Later, during further investigations into the Vex, Osiris and Sagira discover various Simulations on the Fallen and Cabal that would provide valuable information for the Vex in defeating them. Osiris sends the Guardian to prevent these simulations from being completed and destroy the data they desired. However, during a foolish experiment, Osiris revives Dendron, Root Mind as he believed he could control it but it begins to fill in for Panoptes within the Infinite Forest. Calling on the Guardians once again for aid, they travel to the Simulant Past and succeed in destroying Dendron for good.

Sometime later, in the simulant future, Osiris hovered in the ruined Lighthouse alongside Sagira. He suddenly felt massive tremors and encountered an unknown massive entity on the planet.

Quotes

 * "Crota's spawn will snuff out the worlds of Light, and Oryx's coming shall be unfettered."
 * "Every end crawls from the same pit, rising from the schism to swallow matter, Light and life. It cannot be stopped, but here, it can be slowed. The Shrines of Oryx must be destroyed."
 * "If the Vex succeed, it's the end of everything."

Trivia

 * Osiris is presumably named after the god of the same name, the Egyptian god of the afterlife, the underworld and the dead.
 * Osiris was intended to appear in the original storyline of Destiny. He would act as a mentor to the player, and be found in an ancient Vex temple on Mercury. He was accompanied by a robotic assistant, who would later be re-purposed as The Stranger. At the end of the Curse of Osiris story campaign, he calls his Ghost "little light", a name the Stranger also called the Guardian's, suggesting they may have crossed paths in lore.
 * The voice actor for Osiris in Destiny,, also voiced the narration for the Pathways out of Darkness ViDoc. It is unconfirmed if the narrator is supposed to be Osiris.
 * Osiris was the name of a Guardian Faction during the game's pre-alpha phase. It was changed to the Cult of Osiris, though it is not a faction that can be joined.
 * Due to his reputation, nearly every Vanguard veteran has a poor opinion of Osiris. Saladin expressed disdain towards him for nearly ruining the Warlock Vanguard and even his former student, Ikora, has called him the most notorious Guardian in Vanguard history. As it turns, Osiris would later turn out to have heroic tendencies, now working as a protector of humanity from the Vex.
 * However, many have credited him as the greatest and most powerful Guardian in history. Ghost had even mentioned him as the "Zavala before Zavala".

List of appearances

 * Destiny
 * House of Wolves
 * The Taken King
 * Destiny 2
 * Curse of Osiris