The IsoDidact, born Bornstellar Makes Eternal Lasting, was a Forerunner of the Builder rate who became a key player in the Forerunner-Flood War, including the firing of the Halo Array. Known as Bornstellar as a manipular, he had an insatiable desire to search for treasure in the universe, eventually stumbling on the cryptum of the Didact on Erde-Tyrene and releasing him from his 10,000 year seclusion. Following his resurrection, the Didact took Bornstellar with him to investigate the state of the galaxy, coming upon the remains of Charum Hakkor following the firing of a halo decades prior. Needing someone to share his experiences with to try and understand what he was seeing, the Didact performed a brevit mutation on Bornstellar, rising Bornstellar to first form, and eventually turning him into a nearly identical copy of the Didact.
Following Charum Hakkor, Bornstellar and the Didact were captured by the Master Builder at Janjur Qom, and Bornstellar was sent back to his family. Soon after, the Master Builder was charged with crimes against the Mantle, and Bornstellar was brought to the Forerunner capital world of Maethrillian to testify. Soon after the trial began, however, Mendicant Bias and the Primordial attacked the capital using Installation 07, killing nearly everyone on and around the planet. Bornstellar managed to escape, however, and ended up meeting the Librarian.
With the disappearance of the original Didact and Bornstellar’s imprint of the Didact and his memories, Bornstellar became the IsoDidact, while the original Didact became the Ur-Didact. The IsoDidact took command of the Forerunner military, first hunting down Mendicant Bias and the Primordial, decommissioning the former and destroying the latter. He then proceeded to lead the Forerunner’s fight against the Flood, though his efforts were ultimately futile. After the loss at the Battle of the Greater Ark, the IsoDidact traveled to the Lesser Ark, where, after exhausting all other options, fired the Halo Array, killing everything in the galaxy and eliminating the Flood.