Uriel was one of the Archons who was tasked with guarding the Mask of Eternity. He was one of Lucreto's former acolytes.
Background[]
He confronted Lucreto after the Archarchon betrayed the acolytes and tried to take the power of the Mask for himself. However Uriel failed and Lucreto turned him and the other acolytes to stone. Lucreto could yet hear his thoughts as they continued on in the hopes that the Champion Eternal would show up to save them. Lucreto mocked Uriel saying that all of his hopes would fail as he controlled the power of the mask. He appeared to Connor in spirit several times giving him advice and passing on more of the prophecy. Though Lucreto could do little about it, he was quite angry at Uriel's interference.
Behind the scenes[]
Uriel's name is only given during a single flashback recorded in a crystal. In the credits he is simply known as Archon. Although his spirit appears in other parts of the game, he never mentions his name to Connor.
Uriel is based on the archangel Uriel. The archangel believed to guard the Gate of Eden with a fiery sword in some traditions. Thus it is possible that it was Uriel who left the Flame Sword for Conner in the Frozen Reaches, knowing that the chosen one would someday need it. In other traditions Uriel is the angel of repentence, that guarded the jews who put blood above their doors from the angel of death, Azrael (apropos considering that Azriel appears in the game as well). Uriel is also associated with warning about cataclysms such as the Flood, which may also relate to his purpose in the game, warning Connor about problems caused by the cataclysm.
Perhaps he is the Lord of Sunshine opposed to Lucreto (the potential Lord of Darkness).