Prophet of Solemnity

This unidentified Prophet was a San 'Shyuum of the Covenant Empire. It is unknown for certain what rank of Prophet he was, but he is shown giving orders to Sangheili throughout the duration of The Duel. He is presumed to be a Hierarch due to the fact he sits in a Gravity Throne, along with a crown, which the High Prophets wear.

Background
Due to the heresy of the then-current Arbiter, Fal 'Chavamee, this Prophet ordered the execution of 'Chavamee and his wife, Han, both of which were personally orchestrated by the loyal Elite commander Haka. The Prophet decreed that the title of Arbiter, previously one of great honor, would become a mark of shame (further evidence that this Prophet was a Hierarch, as it is unlikely that any lesser Prophet would wield such power, especially in the earlier days of the Covenant). It is directly because of this Prophet that the rank of Arbiter changed from an influential and revered general to a recklessly suicidal warrior meant to help restore some measure of a disgraced Sangheili's tarnished honor.

Trivia
This Prophet greatly resembles the Prophet of Truth in both appearance and personality. He is even credited as such in the Japanese language version of the episode. This may suggest that he was the namesake of the latter Prophet, as the Hierarchs choose their names from those of one of their predecessors. However, as he is simply credited as "the Prophet" in the English dub of the episode, this theory is of dubious canonicity.