The Undying Mind

"When the Undying Mind is threatened, its ancient creators step through time portals to defend it, ensuring that it will continue to thrive, until the Vex once again control the Black Garden."

- In game description

The Undying Mind is an ancient Axis Mind of the Sol Divisive Vex, serving as the final boss of the eponymous Strike and later the main antagonist in Season of the Undying. Its purpose is to protect the Black Garden from intrusion by sealing it out of space and time and to restore the Black Heart.

Early history
"We are starting to believe that time is home to the Vex, and somewhere in those unmappable voids dwell their undying minds."

- Maya Sundaresh. Long feared by the Vex, the Undying Mind was created by the Precursors eons ago and has laid dormant in the channels of the Black Garden since. The ancient Hydra gets its title from its immortal Vex programming, making it seemingly impossible to destroy permanently. Its existence had even became documented by Maya Sundaresh and the Ishtar Collective.

Sealing The Garden
"The Black Garden may not stay among us for long. Something has begun to repair the schism torn by its destruction. Vex now flood the Garden channels to protect it. We must stop the weavers before they seal the Garden and begin to summon back its heart."

- Ikora Rey

Several months after a Guardian found entry into the Black Garden and destroyed its heart, the Undying Mind awakens to seal the Garden away in Darkness once more. Its secondary directives are also to restore its birthplace by summoning back the Black Heart; an act that would result in the destruction of the Traveler. Deep within the garden, the ancient Vex Mind weaves the fabric of space-time around the realm while the Vex gather from across the gate network to protect it.

Deep scans of the growing surge of Vex activity reaches the Hidden lead by the Warlock Vanguard Ikora Rey. With its readings matching no temporal functions, Ikora uncovers the ancient Mind responsible for sealing the Garden and resolves to deal with it accordingly. She begins mapping out its pathways with fragmented data from the Ishtar Academy's archive and successfully pinpoints its hidden channels, with the aid of Cayde-6 and Zavala. A fireteam of Guardians is dispatched to the Black Garden at Ikora's behest to face the Undying Mind, while dealing with a growing number of Sol Divisive Vex protecting it. With the ancient Mind under threat by the Light-bearing intruders, swarms of Precursors are summoned to defend it with a massive Divisive Oculator barring the way. The Guardians kills the Cyclops and its Precursor army as they proceed to an open Vex gateway and disrupt the nearby Confluxes. The Undying Mind is successfully drawn out of the gateway along with armies of Precursors to defend it, but it is destroyed nonetheless.

True to its name, the Undying Mind would not stay dead for long. It would come back from its destruction to seal the Garden yet again, forcing fireteams of Guardians to confront the immortal Vex mind for no end until the events of the Red War. The arrival of the Red Legion would push the Cabal to retake the Meridian Bay and destroy the only gate to the Black Garden, sealing it off once more and completing the Undying Mind's objective for it.

Season of the Undying
"When Guardians last faced the Undying Mind, the Vex were trying to seal the Garden to resurrect the Black Heart. The object of their worship. Darkness incarnate. I wonder if that's still the case… or if the Pyramid forced a change of priority."

- Ghost

An undetermined amount of time would pass outside the timeless Garden as the Sol Divisive Vex lie patiently in wait for the Witness to return power to them. During this time, the inactive Undying Mind became buried in a barrow of flora growing around it. Their prayers would be answered as Darkness returned to their realm in the form of a distant pulse sent across space-time by the Lunar Pyramid's awakening, empowering the Vex within the Garden yet again and causing the Mind to stir once more. With their faith rewarded, Vex Goblins write more circuits to weld to the Mind, building it up to take advantage of their newfound power.

The Undying Mind re-establishes itself after a group of Guardians launched an excursion through a gateway found on Luna and destroyed the Sol Inherent Minds. With the Black Garden lying open yet again, the ancient Mind directs the Sol Divisive's activity in an ongoing offense to claim the Moon for the Vex; drawn to the dormant Pyramid buried beneath its surface. In addition, it began hiding in multiple co-occurrent timelines, making copies of itself in hundreds upon thousands of different realities to evade the Guardians.

The Mind was considered unreachable until Ikora Rey constructed a modified Vex gate built from Vex chasis components, which she and Zavala had tested by killing two dozen of its copies. This allow the Guardians to draw the ancient Hydra out of the timelines it established and destroy it once again. However, as multiple copies of the Undying Mind existed in the timeways, the Guardians had to summon every single copy one at a time until all were destroyed in a matter of weeks. With the destruction of the Undying Mind, however, the Guardians had changed the course of history: the Vex's projected futures from the Infinite Forest gave way to one of subatomic annihilation by the Black Fleet; which was witnessed by Osiris.

Gameplay
"Interesting, undying, huh? What do you suppose they meant by that." "I'll alert the Speaker. Let's find out."

- Cayde-6 and Zavala

The Undying Mind is a unique Hydra in that it has three shields instead of one. When it first spawns, the passage which the player came from will be blocked, ensuring that there is no escape. It also has the ability to "detonate" when a Guardian gets too close, instantly killing them, and can summon endless waves of reinforcements, and while doing so, two vertical confluxes will send out blinding waves of energy to disorient Guardians. It is otherwise functionally identical to Hydras in that it is capable of blasting through a Guardian's shield very quickly with its Aeon Maul.

Trivia

 * While the Undying Mind's Aeon Maul blasts are orange-colored (Solar) the killcam clearly shows they are the same as ordinary Torch Hammers or Aeon Mauls (Void). This may be a developer oversight.
 * The Undying Mind is the third Axis Mind to return. Sekrion, Nexus Mind and Dendron, Root Mind being first and second respectively.
 * The Undying Mind's appearance in Destiny 2 has been slightly altered, bearing a resemblance to The Templar.
 * Despite the Undying Mind being part of the Sol Divisive, Precursors are seen protecting it in Destiny 1. This may show the desperation of the Vex to keep the Undying Mind active as to bring forth models from other times to protect it.
 * The Undying Mind is one of the few characters in Destiny that the player canonically kills multiple times.

List of appearances

 * Destiny
 * The Dark Below
 * Rise of Iron
 * Destiny 2
 * Season of the Undying
 * Season of Arrivals