Aeternus felt pain immediately as Chaos energy bypassed his soul defense and entered his soul. It began wreaking havoc as it is wont to do. It reminded him of his days as an unborn fledgling. The pain was that bad or maybe even worse. His Chaos energy has grown just like he has. It is currently in the divine rank with enough power to erode Authority itself so his powerful soul is not immune to its effects yet.
Chaos energy tried to gush into his soul without restriction so he had to funnel it through a narrow path eroded in his soul to the soul sphere. The pain is worse than having something sharp used to pierce his soul. It threatened to cloud his mind but he held on with the promise that his suffering shouldn't take long. The test shouldn't last more than a few seconds before he has to shut off the flow of Chaos energy. So he had to endure for a short while before the pain is over.
