Evan's conversation with Lios went surprisingly well, far better than he could have expected, and that was due to two main reasons.
First, it seemed that 'Aidos' had already spoken to Lios regarding Evan's plans. Secondly, Lios himself was far more agreeable than any of the Iremith Ouroboros dragons.
What's more, despite how absurd it sounded to everyone he had explained it to, the plan Evan presented to Lios was one meant to save the lives of the planet's people. It was a plan that opposed the Demonic Hand's actions and would slow their efforts to break open the dimensional rift on the Dark Continent.
Because of that, Lios was more than willing to cooperate with Evan. After all, this was the same Ouroboros dragon who had willingly fused himself with the planet's World Tree when the damage it suffered at the end of the Great Valmone War had worsened to the point it was on the verge of collapse.
