Ord Casto, better known as the Prophet of Truth, was born in 2396 on High Charity. He was initially the Minister of Concert and then later the Minister of Fortitude before eventually rising to the rank of high prophet of the Covenant along with the Prophet of Regret and the Prophet of Mercy. The high prophets were instrumental in starting the war with humanity in 2525, and continued to push for their destruction through the following decades. He faced his undoing in 2552 after implementing his plan to replace the Sangheili with Jiralhanae as Covenant commanders and become the only Covenant prophet by letting the other two prophets die. His plan began the Great Schism, which was key in turning the tide of the war and giving humanity the chance it needed to win. Truth made a last-ditch attempt to win the war by travelling to Installation 00 and activating the Halo array, but his actions were stopped and he was killed by Thel 'Vadam.