The flame mentioned by Dark Butterfly is undoubtedly the power of incineration from the Talent Tree.
Earlier during the fierce battle with Jiu Ying in Lu Ye's Divine Sea, she gained some benefits while being burned by that flame and has been craving for it ever since.
Lu Ye was indeed surprised; the soul body of Dark Butterfly wasn't affected by the incineration from the Talent Tree, which didn't make much sense.
Logically speaking, the soul body of Dark Butterfly, being a foreign entity invading his body, should have been treated the same way as Jiu Ying's soul body.
Yet, that wasn't the case.
After some thought, Lu Ye felt this was likely attributed to the Chains of Life, which closely bonded his soul body with Dark Butterfly's under the effect of the Dao Runes, sharing life and death. Evidently, the power of incineration from the Talent Tree regarded her soul body as an ally, not only not harming her but also benefiting her.
