Zatiel's body shook while blood came out from his three eyes, his brain burned with a fever so high that parts of it were being calcined. His vitality was affected and his blood evaporated which made him adopt the form of a mummified corpse.
While this happened, the All-Encompassing Sun Flame filled every single one of his cells and used the Law of Life in his bloodline to fix the damage in his body. Most of his power focused on his vital organs and made sure no permanent damage was left.
Great amounts of energy were being drained from Heaven Swallowing as his brain passed through a constant cycle of destruction and regeneration.
The reason for the Neo-Demon's damage was the use of the discipline of Clairsentience on a level higher than his Rank as an Animus allowed him to do.
