It's not him!
The moment Master Merlin was summoned into the arena, he detected the symbiotic contract between Pei Yan and Hu Jiu, under which their souls and supernatural powers could be shared and exchanged. Thus, when Merlin saw the mechanical duplicate capable of launching supernatural attacks at first glance, he thought not about Pei Yan escaping, but rather that Hu Jiu's soul had entered the mechanical puppet in the arena, continuing the attack to buy time for the genuinely trapped Pei Yan to escape.
However, after a recent examination, he found that Hu Jiu's soul hadn't left his body, and apart from some unusual fluctuations in the source energy, there were no other strange changes. To be on the safe side, Merlin even checked the status of every investigator in the investigation hall, and finding none showing abnormalities associated with soul detachment, he began to doubt whether there were errors in his previous attack.
