"Eirena. Know that you possessed the greatest potential of all your sisters, and so I chose you. They gave their lives so that you could survive and fight in the most important battle to come. They did this willingly, and their sacrifice is not a burden, but a gift to you. Live. Fulfill the destiny for which I trained you, and for which your sisters died."— The Prophet(src)
The Prophet is a title (true name unknown) of an angel who has founded the Hand of the Prophet approximately 1500 years prior to the End of Days. To his followers, he appeared as a human, hiding his true identity.
The Hand of the ProphetEdit
The only source of information about the Prophet are Eirena's memories, as well as those of her other sisters. She tells the Nephalem upon their meeting that the Prophet found them as girls, saving her and her sisters from the curse of Vizjerei mages, and training them in magic. The Prophet, appearing as human, told them of the great danger coming in future, and after training, has put all the girls (except Lysa) in dreamless slumber, for them to awake when the time is right. When Eirena has awoken, the Prophet was nowhere to be found.
Eirena spoke highly of the Prophet, worshiping and revering him. However, she also noted that he had a sense of humor, although she refused to tell the Nephalem what exactly was that hilarious thing he said about the future savior of humanity. She also noted that the Light of Seraphim emanates from Tyrael, just like the one she felt radiating from the Prophet, leading her believe that he might have been an angel as well.
During her journey to the High Heavens, Eirena found a dying angel and received a scroll from him. The ancient script described the Prophet's plan to prepare human followers for his schemes, and confirmed her suspicions that he is, indeed, an angel, working on behalf of the Sanctuary in absolute secrecy.
Reaper of SoulsEdit
As Eirena and the Nephalem progress through her storyline in Pandemonium, in a secret place, they find memories of other sisters of the Hand of the Prophet, as well as Lysa, who sheds light on the Prophet's true intentions. Foreseeing the future, the Prophet knew that only one of the Enchantresses (Eirena), being the strongest, will survive, to carry out his will, while the rest will give their lives for hers. Lysa refused to do so and betrayed the Prophet, but could not kill Eirena due to the binding spell.
After Lysa's death, the Prophet's voice reached to Eirena one final time.