Zaos failed in saving two important people to him, but he wouldn't fail again. He would die trying to succeed… The enemy was clear, and he just had to wait for the demon to show up eventually. Zaos will kill it because he knew that he would show up anyway, even though he would try to prevent his revival.
While Zaos was angry and sad, he realized that the problems of that world, all that suffering, had been caused by the demon god. The humans were guilty for letting their fear force them to do heinous things, but the demon had to pay for his share of the trouble caused as well.
"Are you ready to do this?" Zaos asked.
"Yes… I won't fail Ameria," Aleni said.
"In that case, wait for me outside the city with my horse," Zaos said. "I have to do something."
"What exactly?" Aleni asked.