So who is the Emperor of STO's Tarran Empire? The description assumes it is a male and it says he took on god-like powers.
So add a line below with your conjecture including a logical reference from either the TV series canon or from STO canon. I'll start with two:
1. It's Q. Simple as that. He has a universe to play god in with impunity. Because it's a mirror of the Prime, the Continuum doesn't mind. They let him have his fun here and he leaves the Prime alone... mostly. 2. It's Wesley Crusher! After Mirror-Traveler opens Wesley's mind (in a situation different than we saw in "Journey's End" of course but not completely dissimilar) Wes kills the Traveler and uses his ability to manipulate time and space to rule the galaxy. 3. Mirror-Barclay encounters the Mirror-Cytherians who augment his intelligence, making him more powerful than any other human. 4. ...?