Nonsense. He had no reason at all to save the child. Especially since introduction of the beast suggested that he just woke up or something and may be lazy. He also did not really need an army for anything, if he wanted, he could have continued the rampage and that's it. I mean, he even said that he would do that before killing the king, so why? There is zero logic in the so-oh-powerful beast, who just promised to destroy humanity to suddenly change mind because of some infant, regardless of whether the child is at fault in anyway or not. Because the beast probably killed a couple dozens of other children while destroying the frigging city! The cliffhanger was good, but not good enough to compensate for 40 minutes of this idiocy.
