Fight to the death until one remains. Isn't that literally how demon cults and blood cults train recruits in these stories. I always thought the Tang Clan at least pretended to be orthodox/righteous. This is a downright evil and demonic practice. Seems highly questionable that all the elders would just go along with this psycho behavior. Why kill off an entire generation of talent when your family has already fallen? It's clearly an unforced error, even from a completely ruthless/utilitarian viewpoint.