The true Underworld Servant is still within the Sea of Sinking Light. His true power must be far, far greater than that of his avatar. According to the levels of cultivation, to create an avatar, one must have at least endured the Fifth Thunder Tribulation and reached the Wandering Soul Realm. But that is merely an illusory body, not a true external dharma-body. The Underworld Servant is likely at that very level. Therefore, his avatar can only possess others, borrowing their bodies to gain strength.
If the angel on the sea is also an avatar, it is clearly much more powerful than the Underworld Servant’s. One wonders just how many angels the Sun Holy Cult’s Angel Legion truly possesses.
"Heretic, do not resist! The sacred radiance can wash away the Underworld King’s mark upon you. Throw away the dark artifact in your hands and let it sink into the Underworld along with your sins! You shall be sublimated in the holy light! Your soul shall rise with the sun and exist in the light forever!"
Chapter 316