Why did Taishaku-ten kill Karyoubinga? I understand that he might have brought her to his Palace so that Karura-ou would come over and he could keep an eye on her... But why make the girl sing until she died, and why give her corpse to the dogs? If he hadn't done any of that, Karura-ou wouldn't have turned on him and several deaths could be avoided. Was there any reason as to why exactly he did that?
As far as I can tell, it's because Taishakuten gets a kick out of causing people to suffer. Shorter, crasser answer: He did it because he's a dick who could.