A mysterious masked figure and the supposed emissary of the Goddess, The Prophet is a highest-ranked person amongst the Azadi, regarded at least as equal to The Six. His true identity has been the subject of much speculation for years. During the events of Book Five: Redux it is revealed that behind the mask is Brian Westhouse, posessed by the Undreaming, and he's the one who orchestrated genocide of the magical races -- in order to reunite the Arcadia and Stark, and return home.
A mysterious man in a black cloak seen by an eavesdropping April Ryan to be giving orders to Sister Sahya. She comments that it is odd to see an Azadi woman taking orders from a man, and the Emissary actually seems worried. The Prophet does not speak audibly - in fact, his voice is just a series of whispers. Some might say it resembles the speech of the Draic Kin, as it seems very quiet and sibilant. Given the Azadi's devotion to the Goddess, it would seem that he is a prophet for that divinity. He also appears to walk quite carefully, as if he has been lamed at some point in his life.
The Prophet does not just command the obedience of the Emissary, however, as he seems to hold some influence over The Six. It is he who ordered the assassination of the Scorpion, as part of the Azadi's imperial conquest of the Northlands. This seems to be part of the grand prophecy by which he holds the Azadi in thrall. When Kian leaves the Six, they say of his mission: "The Prophet was adamant. There is much resting on this task. It is the last obstacle, the Prophet said. When it is done ... The light of the Goddess will wash across the world like a tidal wave, drowning all those who lack Faith." He also appears intent that the Azadi Tower be finished in time for its planned inauguration. Given what we see at the end of the game, it is likely that he is the one who originally suggested the construction of the Tower.
The Prophet knows of the caves under Marcuria and seems able to command the Grubbers who live in the catacombs. He also seems to make himself unnoticeable, as he walks into the crowded Journeyman Inn and then apparently vanishes, even before the eagle-eyed Benrime Salmin, a Seer. He also seems privy to the "Banda Magic" the Grubbers wield to open doors in the ancient ruins. Following him, April is led to the Dream Vortex beneath the Azadi Tower, but he then seems to disappear. His knowledge of the Dream Chamber beneath the Tower (with its 'blueprints' of the Tower) encourages the theory that he was the major catalyst in its construction.
The identity of the Prophet has been the subject of much speculation. In Book Five: Redux, the Prophet was finally revealed as Brian Westhouse, posessed by the Undreaming. He is clearly held in both awe and fear by the Azadi, and is regarded as ranking at least equal to the Six. He has a personal interest in the construction of the Azadi Tower, particularly that it is completed on time, and wields at the very least a small degree of magic (enough to open the tunnel into the caves), which is unusual for someone aligned with the Azadi.