Long Chen didn't know, but the Heart Demon's anger amplifying property was merged with his soul during the Soul Transmigration. Now it didn't only amplify his anger when it wished, but it always did.
It was more accurate to say that anger was now a part of his characteristic, at least when it came up Long Chen's second soul that was in this body.
His main soul was unaffected by it. In fact, Long Chen's main soul didn't need to worry about it at all since it's heart demon didn't have anger even if it became active. In a way, the real Long Chen had unintentionally dumped his anger on this body.
The anger of his other body was permanently increased.
****
Unaware of what was happening to his other self, the Main Soul of Long Chen was still inside the Bloodline Temple.
Long Chen had decided to open the second door and take the risk. He didn't know if it was actually going to be worth it or not, but he didn't want to have the regret of not taking this risk.