The theory that the Flame Reaver is a different version of Phainon is driving me insane, actually. The sun versus moon motifs, the Flame Reaver's pursuit of the core flames, plus Phainon's questionable history point to this eventuality. It also upholds the theme of duality introduced in Amphoreus.
Plato's Allegory of the Cave ('coincidentally', the name of the first Amphoreus album) explores ideas of reality, perception, and how one confronts the truth. In the story, a man learns everything he's ever known is fabricated. When he steps out of the cave and into the light, he sees his true reality. He later returns to the cave but finds his eyes adjusted to the light, and can no longer see in the dark. His fellow prisoners think he's gone mad and threaten to kill him if he tries to take them out of the cave.
Anyway, I'm obsessed with the idea that a version of Phainon, the Deliverer, learns the truth that Amphoreus/the Prophecy is fabricated. Instead of embracing the truth, he returns to the cave (his former reality/ignorance), becoming the Flame Reaver.