Adrian's large body melted any physical attack or object that comes in contact with it. This made it the perfect shield when it comes to dealing with the attacks that the Corrupted Yellow Emperor is using. Even if the attacks of the Corrupted Yellow Emperor still have some traces of magic in it which damages his hyper corrosive body, Anastacia with Saena's support would just easily recover all of the health lost.
Seeing the healers in action, the Corrupted Yellow Emperor tried to kill them as well but Adrian easily split apart a smaller version of his current form to send towards Anastacia as protection. For Saena, she could easily hide inside the nether domain when she uses what she learned about energy from the memories she got from the Vermillion Bird.
