Centuries ago the Phoenix People settled on a mountain that came to be known as Mount Phoenix. It is quite close to Mount Jusendo, the wellspring of the various cursed pools of Jusenkyo. The largest source of fresh water atop Mount Phoenix was a Jusenkyo Spring of Drowned Bird, and after generations of using it for drinking and other uses, the Phoenix People became a race of bird-folk, possessing the bodies of humans, but hands and feet that resemble the scaly talons of birds, fully functional wings on their backs. They can also communicate with birds and use them as their servants.
Now considering themselves seperate from humanity, the Phoenix People grew arrogant and contemptuous of "landlings", avoiding almost all interaction with them that did not involve either outright hostility or, far more commonly, the usage of their magical Imprinting eggs to encase and enslave them. What little interaction with humans was carried out in secret, the Phoenix People using Nanniichuan and Nyanniichuan to assume ordinary forms that they could use to infiltrate human society.
The name of their tribe comes from their leader, Saffron, who himself has traits in common with the legendary phoenix. He is an innate wielder of powerful, mystical flames, capable of devastating fire attacks or producing heat and light for his people, the predominant usage of his powers. Like a phoenix, Saffron can reincarnate as an egg that will hatch into a baby version of himself if slain, but it is unknown if the previous "Phoenix Kings" were past incarnations of Saffron, or if they breed like normal beings and can only reincarnate if slain by violence.
While it is unknown where Saffron came from, he is clearly even more closely bound to Jusenkyo than his followers. In order to attain his full form, specifically to attain it and not be the victim of a power overload that will eventually destroy it, he needs to undergo a mystical bath that requires temporarily diverting the waters of Jusendo. This causes Jusenkyo to dry up while Saffron is undergoing his bath, but the pools will be restored unharmed once Saffron has finished the ritual. It is a misunderstanding of this fact, resulting in the belief that Saffron is going to destroy their chance to be cured, that brings Ranma Saotome and the other cursed characters to oppose Saffron. However they develop personal reasons to fight him as well quickly enough.