[@Archangel89] - It's a bit more complex than that. You see, only a Divine Cord can control a domain. A god is built up from the Divine Cord and up in this order:

Divine Chord -> The Mind -> The Physical Form.

Thus, any form of divine power which affects a god changes them in an inverse order like so:

The Physical Form -> The Mind -> Divine Cord.

Thus, Iarus would need to be inside the aura for long enough for the fear to alter his body and mind before it could start to alter his Divine Cord. Now, altering one's own Divine Cord is a dangerous matter. Saturate it too much and he could lose his former domain to the new one entirely. If his Divine Cord is only mildly affected by the divine power then the foreign domain may flavor his current domain. This effect will wear off over some time as a single cord can only hold one domain and will reshape itself around it's primary domain.

More than that I cannot say until it becomes relevant to the story lest I spoil the efforts of discovery.