Jusenkyo, the Pools of Sorrow
In the Mt. Bayankara range of the Qinghai providence of China, there is a valley. This valley is host to a thousand natural springs, each full of magical water. In the majority of the pools, something or someone has drowned. Usually in an impossible manner.
And this is Jusenkyo, the place of cursed water. Should anyone fall into those pools and NOT drown, they will take the form of whatever drowned last in that pool when splashed with cold water. They will stay in that form until they are splashed with warm water, and then they will return to their original shape.
There is arguably a cure for obtaining a Jusenkyo curse, which is actually VERY, VERY high-level magic (meaning it's not a curse someone could expel with different magics without dire consequences: Things like the Triforce, Silver Imperium Crystal, or Dragonballs might make it possible, but not without backlash of some type). The natural cure, of course, is for that person to find the pool of their gender. Either Spring of Drowned Young Man, or the Spring of Drowned Young Woman. This would also have to be a full-body dipping, because curses CAN be mixed (Tarou demonstrates this later in the manga by acquiring tentacles on his already-mammoth form, via Spring of Drowned Octopus).
There is also a great deal more to Jusenkyo than just the pools. The valley itself seems to be mystic, as there are many items derived from its origins (water-proof soap, instant curse powder, water veins that actually go all over the world--several in Japan, though they are now inactive). The water of Jusenkyo itself has very magical properties, and remains the lifeblood to both the Musk Dynasty, who neighbors the Juketsuzoku borders, and the people who inhabit Mt. Phoenix, which hides the source of Jusenkyo's water: Jusendo (and the Dragon and Phoenix Tap reservoir that lay within). This is the foundation on which more of the heavy plot-related adventures of Ranma 1/2 is built from.
Also, canon has established that Jusenkyo magic can and WILL affect downlines. The Musk Dynasty and the Phoenix People are a direct result of Jusenkyo. Certain genetic traits are bound to be passed down--the Phoenix people used water from a spring (Spring of Drowned Bird) at the base of their mountain as their water source. They developed aviary traits over time: talons, clawed hands, and functioning wings, as well as the ability to communicate with and control birds.
There are several high-level magic items that have directly to do with Jusenkyo, or Jusendo:
Chiisuiton "stopping water bucket" - This item, a water ladle, is a Musk Dynasty treasure. It's used to lock creatures in their cursed forms permanently. Anything with a Jusenkyo curse splashed with cold water from the Chiisuiton will remain in that form. The Musk use it as a means to breed with animals to create blood limits (Lime has the traits of a wolf, and is naturally fast--much faster than Ranma. Mint has tiger traits, and is stronger than even Ryouga. Herb has dragon's blood, and can wield and manipulate massive amounts of ki).
Kaisufuu "open water pot" - A kettle, and the curing item to anyone under the influence of the Chiisuiton. When hot water from the Kaisufuu is poured on someone, they lose the locking ladle influence.
Kinjakan - One of the reservoir keys to Jusendo's tap. Passed down by the Phoenix people, it's used to turn on the hot water of Jusendo, or the Phoenix Tap. This hot water is crucial for the ascension of Saffron, who uses it to become a full adult, able to manipulate his powers properly. It it a hoop connected to a staff with handles--it's also a very dangerous weapon, as the hoop can be thrown to bounce off of or cut through objects. It can also generate a tremendous amount of heat.
Gekkaja - One of the reservoir keys to Jusendo's tap. It remained in it's place in the Dragon Tap, a half-moon blade on a staff identical to the Kinjakan's. The difference is that instead of heat, it's capable of freezing whatever it touches. During the fight with Saffron, Ranma bent the blade so that it more resembled a garden hoe than a staff. The blade, however, is exceptionally sharp, and able to cleave just about anything.
For archiving purposes and maybe potential plot crack later on (there's a lot of Jusenkyo-enabled threads within Ranma 1/2), I'm keeping a tally of people who've fallen into the camp springs. This way, if there IS a push on something to do with the springs, I can contact everyone that would potentially be involved for full approval of said potential ideas.
Victims of Jusenkyo (and curse)
Ranma Saotome (Spring of Drowned Girl)
Yachiru Kusajiri (Spring of Drowned Penguin)
Neji Hyuuga (Spring of Drowned Mermaid)
Uryuu Ishida (Spring of Drowned Duck)
Ryuuken Ishida (Spring of Drowned Alien Frog)
Lu Xun (Spring of Drowned Girl)
Jouichirou Nishi (Spring of Drowned Cat)
Ari Ruka (Spring of Drowned Mouse)
Ash Ketchum (Spring of Drowned Puppy)
Alphonse Elric (Spring of Drowned Cat)
Fakir (Spring of Drowned Duck)
Victims Known to Ranma
Neji
Yachiru