He wasn't worried about himself but for the people back on Saint Monster World, the world tree is already overworking cleansing the entire world, it doesn't have time to fix the health of the populace, he had already decided that after this, he will return back to the lower planes to make some arrangements.
The trident wielding creature roars as it felt it's strength returning, it then stares at it's opponent and was startled to see that they have the same condition, it knew that one of it's trump card have become less useful because it's opponent have the same ability.
It cannot fight as long as he could, this universe restrict them so they cannot prolong any battle, this is the reason why the other Saint Lords were protecting the giant eye, it's because it had the ability to transform it's surrounding and making it similar to their home universe.