This was a Branding deep within the spirit entity's will, which was naturally obtained once the requirements were met.
In the world of the gods, this was the "Wrath" Godhood, which allowed him to continuously draw strength from the wrath of all beings and grow increasingly powerful.
The most direct experience was that the instant he obtained the Authority of Wrath, he could feel a fine, invisible thread between himself and the dense, evil spirit entities around him. That was the power of the Authority, and as long as they harbored the emotion of anger, it would contribute a thread of strength to him.
Perhaps this power was insignificant, and even when added up from all those around him, it wasn't much, but it was enduring and continuous, and his absorption range would greatly increase as his strength grew in the future.
The stronger the emotion of anger, the stronger the power provided.