He spent the ride back scrolling through the plot from Heimo's perspective. He had mostly gotten it right. The fuse that started the war didn't come from Jingxue-Jun's death, but the death of Heimo's adopted parents, Luqiu couple who had taken Heimo in when he almost died of frostbite. The excessive grief had sent their youngest daughter, Luqiu Ning, into a sort of qi deviation where her body was consumed by resentful energy. There was no way Heimo would sit still and watch his sister dying slowly just like that. Without an ounce of hesitation, he threw away his cultivation to embrace the demonic path and since then, he had become the medium to transfer the resentful energy out of Luqiu Ning's body.
But she didn't recover and she wouldn't, until Heimo opened the gate to the demonic realm.