The Host

Indeed, it was as Sunny had thought.

Mordret had learned his secrets from the mirror shard left behind by his Beast. He didn't really know of his Aspect… he only knew of its reflection.

And that reflection was incomplete.

That was why the cunning prince had assumed that he would be able to enslave Sunny by using his True Name. Of course, Mordret would have been careful, taking the possibility that Lost from Light already had a master into account… but Sunny was half a step ahead. He had doused that caution by being ready to pretend to be enslaved…

And then attacked.

...The Cruel Sight shot forward, narrowly avoiding the mirror fiend's saber and sinking deep into his flesh. It cut through the enchanted black tunic, pierced Welthe's body, and emerged from her back.

Mordret's face contorted, his eyes full of shock and pain.