Seth and Lexi's powers worked together to completely nullify the ethereal flames who threatened to burn his body and soul, creating a final result that was not a bit different from how his flames couldn't harm the purple goddess. They were both unscathed from that first exchange of attacks.
However, it was not something the Ethereal Goddess was expecting to see. She instantly realized that Seth was not like any other average Mana Sovereign Realm practitioner in terms of battling experience and soul strength, since he was able to easily block her disguised attack.
It was certainly ruthless to begin a battle with a soul-destroying skill, but even though she opted to go with that strategy, she had still failed in the end. The fact that a spirit could be helping him out had never crossed her mind and she attributed his strength, to the nature of his aura.
Swoosh!