If he didn't kill the devil now, it might recover. That would only make it more difficult to deal with later on.
If he couldn't kill the devil, he could at least leave the devil exhausted. Maybe the old thing will eventually die from tiredness.
"That old thing should have been dead long ago. He robs prenatal qi just to extend his life over so many years. Now that he's turned into a devil, he's living someone else's life span."
The devil drained the essence and blood of others. By doing this, he added his victims' life force to his.
If he could prevent the devil from draining any essence or blood, they might have a chance to defeat him in a few years. Maybe it would take eight or ten years?
In that moment, Xu Xiao came up with many ideas of dealing with the devil.
Maybe, he had to sacrifice his life to defeat the devil.
Maybe he couldn't see the descendants of Clan Xu grow up or the people of Clan Xu come back home.
