He had realised that he had still been underestimating the capability of True Saints but he wasn't afraid, the world forbids such being to descend and his avatar wouldn't pose that much threat to him since he and his scarabs would be able to devour it's energy.
The only thing that worries him is the number of Saints and peak Xiantian Emperor Realm is quite great compared to the entire force of this world.
If he fights with the avatar, he wouldn't be able to split his attention even for a bit since it would definitely spell doom to him and his group.
His scarabs would also be busy since they are the main weapon against the avatar of the chaos commander in the chaos world.
He could only hope Sans and the others would give him a surprise, if their strength is comparable to Saints then he won't need to worry that much.