My theory is that the horned children from the past two games (Shadow of the Colossus & Ico) were turned into these griffin like beasts, stripped of their humanity, still retaining their most prominent trait. How, i'm still thinking of, I'll update if I can. The species itself is then given back a bit of their own human traits by giving the strange deity at the top of the tower human sacrifices and giving the creatures the essence which revitalizes them and makes them a bit more cooperative. They can live without the essence, but it makes them all the more extraordinary and useful when they do use it. Back to the giving back their humanity, remember in SOTC how Wander was the "first" horned child? What if Trico is a descendant of Wander? After all, Wander did have the ability to fall from great heights, like atop the Colossi and somehow not die, showing some sort of bodily strength that helps him avoid injury. All Trico needed to heal again was some barrels, therefore giving him back a sliver of humanity and healing him, just like how Wander was easy to recover in SOTC. Since Dormin was technically sealed inside the horned children, couldn't it be possible that after enough children were created that Dormin could rise again and attempt to go back to his former glory? He could have turned most of the children into these beasts by combining them with the dead Colossi, taking the most needed traits from the dead bodies like wings and the horns. Afterwards, Dormin led them back to the old land where he was at his height and start building his power again, which led to the Master of the Valley being a sort of holding place for Dormin's resting soul. The children who weren't turned became the rebuilders of the area and brought back the land, until its eventual downfall as seen is TLG. Dormin's soul was still stuck there, as there were no more children to feed off of, so Dormin sent out the turned children to retrieve those who were "lost" or evolved descendant of the horned children (without the horns of course) to try his luck at continuing his mission. Thousands of years pass and the boy from TLG, another descendant is brought and is seemingly chosen to house the near complete Dormin again to begin his reign. This can be infered based on how differently him and Trico are treated in the cutscene after it's revealed how everything occured. If you played the game, you know how that ends. The Master (or Dormin, in this case) is defeated yet again and the cycle begins anew as shown in the cutscene after the credits. Feel free to tell me what you think or add your own thoughts! I'm all ears and willing to debate ^^

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