I just encountered him in PvP. I missed the first special(s) as I wasn't paying attention and only my Thetys was left standing when I looked next so not sure the other monsters are also hacked but it is likely. I next was hit by his Thetys Pet which proceeded with "Mysterious Protector" and followed by "Epic Blizzard". Unfortunately, he currently has no team so can't look him up. His name is Raul and he is using the monster hack. He is at the top my PvP attack list:
I hope something can be done about this guy!
And here you can see my Thetys being frozen and stunned by Thetys Pet: