So... yeah, Ellie's idea? Samantha likes this, but she wants to suggest an addendum.

Completely remove Thiazi's taint.
Remove the bracelet.
Let him go gray and stay gray.
Make him be one of the servants who tends the entrance portal so they can keep an eye on him.

Just in case they need him somehow and there is some small way he can be used against Thiazi. She's also not comfortable destroying him completely, as he might still come back again knowing this world.

Did I ever mention Sam had a mean streak?