@Melancholy Exile and Cerubois:
I think Xaki is referring to the Warrick article. The one where he is captured and tortured by someone (Warrick assumes it was a guy because of his voice) wearing a Zaunite bio-hazard suit. This guy taunts Warrick about all of the children Warrick killed in Ionia. Then he removes his mask and reveals he has a half melted face.
Ultimately you get the idea that this was an Ionian, male, that survived an attack from one of Zaun's Melter squads. If it was Zelos it would explain his disappearance for a while; he would have been recovering from his wounds then going rogue (I assume that last part). It is all conjecture, but it seems plausible to me.