Endurance-of-Will

Endurance-of-Will, referred to simply as Endurance, was a Promethean Warrior-Servant. She was a former lover of the Ur-Didact before his marriage to the Librarian and served as his top lieutenant in the endgame of the Forerunner-Flood war.

Biography
She was romantically involved with the Didact before the human-Forerunner wars, although he would later choose his eventual life-mate outside his rate, marrying the Lifeworker known as the Librarian instead. The Librarian gave the Didact a choice to return to his rate; had he done so, he would have married Endurance. However, he chose the Librarian, a decision that caused Endurance to resent the Librarian for thousands of years. During the war against humanity, Endurance served as advisor to Bitterness-of-the-Vanquished, one of the greatest Promethean commanders and the Didact's mentor. Endurance herself was considered one of the Forerunners' top strategists, often clashing with the Ur-Didact regarding battle strategy.

Near the end of the Forerunner-Flood war, the now mentally unstable Ur-Didact requested Endurance's presence on his primary shield world, Requiem. The Ur-Didact was carrying out his new plan to use the Composer to convert all of his fellow Prometheans — and later humans — into war machines to combat the Flood and later eliminate all species who he might perceive as a threat to Forerunner primacy. Although innately doubtful and deeply worried for the Ur-Didact's sanity, she did not voice these concerns and ended up supporting him due to her code of honor and her intense loyalty to the Didact. She became the Ur-Didact's adjutant and ultimately remained as the last Promethean loyal to him left unprocessed by the Composer, though she was slated to join the others eventually.

When the Ur-Didact returned to Requiem after composing the humans of Omega Halo, the Librarian had followed him, intent on imprisoning her husband in a Cryptum. Endurance confronted the Lifeshaper once she arrived on Requiem and initially showed willingness to follow the Ur-Didact until the end, in part due to her personal acrimony for the Librarian and her stringent sense of duty to her commander. However, her faith in the Didact was not as resolute as it appeared. Endurance eventually agreed to help the Librarian, having accepted the fact that the Ur-Didact was being used as a pawn by the Gravemind and that meditation in a Cryptum might actually benefit him, perhaps allowing his mind to heal via long exposure to the Domain.

After the Librarian knocked out the Ur-Didact and locked him in a Cryptum, Endurance insisted to stay behind and protect him, obeying his final command to protect Requiem with her life. She reluctantly allowed the Librarian to remove Requiem's army of Promethean machines from the Ur-Didact's control and to leave a personality impression of herself within Requiem in order to guide future visitors and warn them of the Didact. Shortly after this, Endurance composed herself, becoming a Promethean Knight and thus remaining as an ageless guardian for the Didact. After Endurance's composition, the Librarian took control of her Promethean Knight body along with the rest of Requiem's Promethean constructs.

Personality and description
The Librarian remembered her as honorable and sensitive and because of this, she believed Endurance could yet be convinced to help her stop the Ur-Didact. Underneath her facade of strict adherence to the Promethean code and in spite of her deep resentment of the Librarian, she was shown to be ultimately rational, never truly agreeing with the Didact's genocidal scheme. Despite this, she still deeply respected the Ur-Didact.

Endurance was small for a Promethean and possessed a catlike grace. She wore uniquely simple battle armor with sweeping curves and none of the decorations or spikes characteristic of Promethean armor.

List of appearances

 * Halo 4
 * Terminals
 * Halo: Silentium
 * Halo 5: Guardians