Great Military Leader
These children, together with their father fought in the Human-Forerunner war. During this war, all of Didact's children were killed, before the Didact successfully captured the human commander Forthencho and ended the war. Since the Forerunners knew yet nothing about the cause of humanities ferocity, the Didact held humanity in contempt. This contempt did not cloud his thoughts about the military leader of the humans, whom he showed great respect.
- “Lord of Admirals... So very many years have we battled... My Finest Opponent”— The Didact to Forthencho upon his capture
Following the end of the war and the first discovery of the Flood, he advocated a policy of vigilance and research in the event of a Flood resurgence. He also proposed the construction of Shield Worlds across the galaxy, in order to monitor the galaxy for Flood outbreaks and provide military support should they occur. However, a faction of Builders led by Faber proposed the construction of a series of superweapons to deal with the Flood instead, and they were successful in convincing the Forerunner Council to sanction their plans. Having lost the political battle, the Didact was stripped of his power and forced into exile.
Adventures in Ancient Times
The Didact went into a state of meditation inside a Cryptum where he stayed for over one thousand years on the planet Erde-Tyrene. Here he was found by a young Forerunner Manipular, Bornstellar-Makes-Eternal-Lasting, who had come there in search of Precursor relics. During their travels, the Didact performed a brevet mutation which imprinted Bornstellar with all the memories and knowledge of him; although they would not awaken within Bornstellar until later on. Shortly after this, when they were intercepted Faber, who interrogated the Didact in order to find the Shield Worlds, or give Faber access to Contender-class Artificial Intelligence, which he refused to give.
Even though most Forerunners presumed that the Didact had been killed after interrogation, he was really put into stasis aboard a ghost ship in a Flood-infested system. Meanwhile, the Didact's personality imprint in Bornstellar's body took full control of him, turning him in a copy of the Didact. After surviving the assault by 032 Mendicant Bias on Maethrillian, Bornstellar met the Librarian on the Greater Ark. In the absence of the Didact, Bornstellar resumed the Didact's duties as supreme commander of Forerunner military due to the present threat of the Flood. After the Didact had spent an unknown period of time in stasis, the system behind it failed due to power failure, releasing the Didact. After his release, he was found by one of his former Promethean Warrior-Servants, who helped him get his bearings. Together they found two more people on the ship, both kept in stasis, and together they took control of the ship, which was still floating in Flood-infested space. However, the ship was quickly spotted and taken over by a large Flood host and the Didact was to be inspected and interrogated by the Gravemind.
Upon first meeting the Gravemind, the Gravemind began to invade the Didact's mind which inflicted unspeakable mental torment to him; the Didact described the process as more of a malediction than a conversation. The Didact only survived because the Gravemind wished him to, it was the Gravemind's intention to release the Didact, with his tortured psyche, to sow chaos in the remains of the Forerunner Ecumene.
After his mental torment, the Gravemind released the Didact and sent him back to Faber's ship. Here, the Didact delivered him the painful message from the Graveming, taunting him with the suffering of his family who had been absorbed into the Flood collective. Seemingly taking pleasure in conveying the news to his old enemy, the Didact stated that Faber and his Halos were to blame for their predicament. After hearing his message, Faber decided to bring the Didact to the core of the Ecumene so he could deliver his message. Against his strongest objections, the Didact was forced to recall his encounter with the Gravemind, which he had partially had suppressed, dealing further damage to his sanity.
In the time that the Didact had spent away from him, Bornstellar's imprinted memories had completely turned him into another Didact. For this reason, Bornstellar was now referred to as Iso-Didact while he would be known as the Ur-Didact. While the Ur-Didact's privileges were restored, he was not granted the command of the Ecumene's military which was residing with the Iso-Didact. Convinced that his old strategies, which were now performed by the Iso-Didact, were viable against the Flood, the Ur-Didact left the capital with his loyal Prometheans and went to Requiem to work on alternative methods. Here the Ur-Didact showed some of the impact of his mental torture as he was applying the philosophy of the Flood in order to justify his actions. The Ur-Didact even began experimental procedures on himself to make him immune to the Flood, one of these experiments left him disfigured.
After acquiring a Composer however, he decided to use it to transfer his Prometheans from their biological forms to war machines, which he believed would allow them to fight the Flood without risking infection. He did not try to compose himself, believing that the device would no longer have worked on his new, disfigured, form. While the machines did little to slow the Flood's undaunted advance, the Didact believed that the issue lay in their inadequate numbers, wholly failing to recognize the sheer futility of the strategy.
After years of experiments, a meeting between the Ur-Didact, the Iso-Didact and the Librarian was planned. During this meeting, the Ur-Didact again showed that his perceptions and views were distorted by madness, as he began to argue that the Iso-Didact's actions and methods endangered the Forerunners. He proposed new, and more extreme strategies that the Forerunners should adopt if they wanted to survive. The Ur-Didact had deduced that Flood had targeted Forerunners as an act of revenge for keeping the humans from the Flood. This led him to believe that the Librarian's favouring of the human race was a profound betrayal to the Forerunner species.
It had become apparent that the two Didacts had become two profound different individuals: The Iso-Didact had started to realise that ignition of the Halo Arrays would become inevitable, while the Ur-Didact was adamantly opposing him, his opposition fuelled by the Gravemind's manipulation. Before this meeting could turn even uglier however, they were notified that their planet would soon be attacked by a huge Flood force. As they made their escape in two separate ships, the planet was attacked by millions of Flood dispersal pods. The Iso-Didact, accompanied by the Librarian, took off to the Greater Ark, with the Ur-Didact following.
The Ur-Didact's Plan and Downfall
While on the Greater Ark, the Iso-Didact set up an emergency conference with all the Forerunners commanders, the Ur-Didact, still convinced of their betrayal, would not come. The Ur-Didact stayed on his ship, and would not fight an incoming Flood attack. During this chaos, he showed his true plan when he took the Composer to the nearby Omega Halo in order to harvest the installation's entire human population. Having acquired the bulk of what remained to the Librarian's human specimens, the Ur-Didact returned to Requiem to implant the human essences into his Promethean war machines. In his maniacal scheme, the machines would eventually defeat the Flood, and Forerunner remnants would unite under his leadership with Requiem as the center of their power. His further plan was to, after the Flood's defeat, eradicate the galaxy of any human and all "suspect" species which could potentially threat the Forerunner's power.
Devastated by the loss of "her" humans, the Librarian followed the Didact to Requiem with the intent to capture him. After a brief exchange on the Mantle's Approach, the Librarian incapacitated him through force and placed him in the Mantle's Approach's own combat Cryptum. After sealing him in the core of Requiem, she hoped that he would spend his time meditating and reflecting upon what had happened. It was her hope that his contact with the Domain would undo the Gravemind's damages and he would eventually awaken. Then he could help humanity take control of both the Domain as the Mantle of Responsibility with the Janus Key. The Librarian then took over the Promethean Knights stationed and gave them orders to prevent any external force from opening the Cryptum.
However, at the final Forerunner-Flood confrontation in their war, the Domain's true nature became apparent to her. It was a Precursor creation and would be destroyed when the Halo Arrays were fired, along with the rest of their creations. After the end of the Forerunner-Flood war by ignition of the Halo Arrays, the Ur-Didact spend his captivity in complete silence, dwelling on his own insanity and rage.
Reawakening and Double Defeat
After the wreckage of the UNSC Forward Unto Dawn crashed into the planet, the human warrior John-117 were attacked by the Librarian's Promethean Knights as to keep them from the Didact. Even in his hibernating state, the Ur-Didact was still in control of Requiem's systems; he used this to lure John-117 to Requiem's core and release him. After his release, the Ur-Didact quickly took control of the Promethean Knights and later allowed Jul 'Mdama's Covenant to coexist. Having spent the last 100,000 in silent meditation, his psyche had fully broken; the Librarian's plans to have him lead humanity towards the Mantle shattered.
Escaped from his imprisonment, he intended to use the Composer once again on humanity and fulfil the plans he had all those years ago. Having fully control of his combat Cryptum, he spent some time preparing his ship to seek and take control of the Composer. After some ineffective interference by John-117, he entered the Mantle's Approach with his Cryptum and plotted a course to the UNSC Research Station Invanoff Station near Installation 03 which housed the Composer. After a short search, he took control of the Composer and used it against all the human scientists and ineffectively on John-117; he had been given immunity to the Composer's power by an imprint of the Librarian. While John-117 had boarded his ship, the Ur-Didact had set a course to Earth in order to compose the human population present. However, shortly after starting the Composer he was attacked by John-117 which resulted in the Ur-Didact to fall into a slipspace portal. Subsequently, John-117 destroyed, and escaped the wreckage, the Composer.
Unknown to the UNSC, the Ur-Didact had survived his fall into slipspace when he crashlanded unto Installation 03's surface. Shortly after his arrival, he was discovered by SPARTAN Team Black. After disposing of them, he travelled to the Composer's Forge and ordered 859 Static Carillon (the keeper of the Composers) to provide him with a Halo Array so he could repair it. Taking one of the Composers present, the Ur-Didact travelled to the Halo, followed by Blue Team. Blue Team was helped by Carillon as he viewed the Ur-Didact's Promethean Knights as abominations.
When the Ur-Didact became aware of Blue Team, he confronted them with the intention to finish them off once and for all. However, during the fight he was stabbed in the eye by John-117, this let the Ur-Didact to lift him in the air and crush his helmet. While fighting the remainder of Blue Team, Carillon attacked the Ur-Didact from behind and teleported in to the Halo's Control Room. John-117 soon arrived in the Control Room with the Ring's Activation Index with the intent to use it for defeating the Ur-Didact. The Didact did not understand why John would activate the ring just to kill him, but John explained that that was not his intent. He used it to disable Halo's safety protocols which gave Carillon the ability to eject a section of the Array into the Composer's Forge. Carillon decided to save John, but left the Ur-Didact to be subjected to the Composer's effects. It was later stated by John that he did not believe the Ur-Didact to have died, but merely "contained".