Hit by Heinald's Death Ray, a big cleft appeared in the Yeti's chest, and that area was completely charred. Although the Yeti's body was very strong, Death Ray's destructive power was too much. Moreover, he was not a newly ascended Ainsar, his spiritual power was far greater than that of a newly ascended Ainsar. Therefore, all of his spells were quite destructive.
The severely injured Yeti started to flee with all his remaining strength due to his survival instinct. Various parts of his body were also burned while he was trying to get rid of the Fire Vines. There was hardly any part of his thick fur that didn't burn.
Normally, Heinald would chase and kill him, but this time he was intent on letting him escape. The weather conditions were already so harsh, he didn't want to waste any more time chasing him. This yeti wouldn't be any more of a problem for him anyway, as his injuries were so severe he would probably die soon.