Prophet of Truth

Summary
The Prophet of Truth is one of three High Prophets that lead the Covenant High Council.

Speculation states he is the youngest of the three prophets, on account of his appearance and voice, but there is little to back this up. He also appears to be the most powerful of the three High Prophets, making him the overlord of the covenant.

Justification of the belief that he is the most powerful of the three high prophets comes from scenes such as the opening cinematic sequences in 'Heretic', and scenes during the opening of 'The Arbiter'. His authority is also clearly exhibited in other ways, for example, it is he who airs the transmisson informing the Covenant that the Great Journey is about to begin (before being interrupted by Master Chief at the start of 'Gravemind').

After the High Prophet of Regret was killed by the Master Chief, he began replacing the Elites with the Brutes as the Prophets' protectors. This ultimately led to a civil war throughout the Covenant.

During a Flood attack, he allowed the High Prophet of Mercy to be consumed by an Infection Form, with the words: "The Great Journey waits for no one, brother. Not even you."

As it looked as though High Charity would fall to the Flood, he fled in a Forerunner Ship. When the Chief questioned dying Mercy, he said that Truth was going to Earth "to finish what we started".

As of Halo 2, Truth is the only High Prophet (and possibly only prophet) alive.

Rise to power
It is widely speculated (and also rather obvious) that he had plans to be the supreme ruler of the Covenant. This is supported by the fact that he let his comrades, Mercy and Regret, die. In Halo 2, he sends a message to Regret:

"Your haste has jeopardized the fullfillment of our Covenant; threatened our grand design, that you shall be spared a public display of our contempt, this thanks only to Mercy and his wise Council."

It is clear that if Mercy had not decided to spare Regret, he would've let him die.

Quotes

 * "Ultimately, the terms of your execution are up to me..."   (to the Arbiter)
 * "Politics, how tiresome..."
 * "The Sacred Icon has been found. With it our path is clear, our entry into the Divine Beyond guaranteed"  (adressing the Covenant)
 * "Kill the Demon!"  (to the Brutes, after Master Chief infiltrated High Charity)
 * "Let him be!" (to Tartarus)
 * "The Great Journey waits for no-one"  (to the prophet of Mercy)
 * "I am the Prophet of Truth and I am not afraid" (adressing High Charity after the Flood infestation)

Related Links

 * High Prophet of Regret
 * High Prophet of Mercy