I was thinking about this last night, and I think it's the Faceless One. I don't believe that Eldor is still alive. And there is no other established good magic user on Eternia capable of doing something like this, other than Faceless One. I don't believe Orko is capable, and Gwildor is a scientist, not a magician.
If it's not Faceless One, then it is likely an Etherian power, like Light Hope.