The Sacred Dragon Palace was a huge sect in the Black Mountain Immortal Realm. The founder of that sect was a powerful man who possessed the bloodline of a true dragon. As such, that sect worshipped dragons and was extremely powerful, making it ranked among the top five in the sect.
Furthermore, the Sacred Dragon Palace specialized in refining all manner of immortal weapons and armors. The quality of those armors was on par with that of the Hundred Creations Mountain.