 The Didact (voiced by Keith Szarabajka) is a Forerunner military leader who is married to the Librarian, and is Halo 4's main antagonist. He develops a deep animosity towards humanity after fighting against them in the Human-Forerunner War. The Didact disagrees with the plan to build the Halo array, and goes into exile in a Cryptum hidden on Earth for years. He is found and awakened by a young Forerunner named Bornstellar. The Didact imprints his consciousness on Bornstellar, who then becomes the IsoDidact; when the Ur-Didact is presumed dead after being captured by the Master Builder, Bornstellar assumes the Didact's role.
