When Auriel lay on Roy's right shoulder, he could clearly feel a sense of despair continuously emanating from her soul. Through her contact with him, his divine spark absorbed this despair, causing the power of his authority to increase slowly.
During this process, Auriel also absorbed the Chaos power in Roy to suppress her Void power and prevent her remaining upper body from completely undergoing Voidization.
Roy could feel that Auriel's despair was mainly for her companions and the High Heavens, not for her life. Although her mind was already blurry, the instinctive disgust and hostility of the creatures of the material world toward the Void gave her the instinct to survive.
This was why Lilith had suggested that he sign a symbiotic contract with Auriel. Auriel needed Roy's Chaos power, and Roy needed Auriel's despair. A wonderful cycle formed between them.