I made a mistake with Ketheric

So.. I turned Ketheric into gold. I wanted to see what happen, if the fight would be skipped or something interesting. And I did it before free Aylin, after I free her I came back to look what will happen now. He was still gold and we just could beat him up. But here's the problem. Like on 40 HP He breaks out of the gold and no cutscene plays or can he actually die. His HP got to 0 but he still lived.. I gladly did a fail save in order if something like this happen but still I would lose some time and progress I would like to not to. Have anyone a solution to get him ot of gold or something??

So.. I turned Ketheric into gold. I wanted to see what happen, if the fight would be skipped or something interesting. And I did it before free Aylin, after I free her I came back to look what will happen now. He was still gold and we just could beat him up. But here's the problem. Like on 40 HP He breaks out of the gold and no cutscene plays or can he actually die. His HP got to 0 but he still lived.. I gladly did a fail save in order if something like this happen but still I would lose some time and progress I would like to not to. Have anyone a solution to get him ot of gold or something??