beta
I've been thinking this for a while, but I think (or at least very much hope) that Maythan is the original Maythan. There isn't much to back it up, but they have similiar personalities/attitudes, look the same, and he has a trauma response to a situation that is similar to what happens when he was attacked before losing his memory. Also it feels strange to have that personal connection to Carsen just taken away.
What if he was the OG Maythan and when he had the accident his soul traveled to our universe, lived an entire life without knowing who he was, and then returned to the moment of his accident.
It's clear that Maythan has a special power and I think he himself is the "Fate Stone" and is able to change fate through the knowledge he learned from his other life along with his power.