Incidental ImmortalsThese are the immortals that Psyche and the Community are aware of. These individuals were not born immortal but somehow achieved it or had it thrust on them. There have been a large number of ways that this has been achieved, and some of them had been achieved through highly unethical means.
The main thing about incidental immortals is that their immortality is not passed on to their children.
Dryads and Oreads
Dryads and oreads are each a possible result of an infection by a dryad fruit (the other two possible results being death and fighting off the parasite). Psyche is aware of close to nine hundred dryads and assumes that there are a few others. There are about 12 oreads known, possibly one or two others.
After eating a fruit from a dryad tree, the seeds will take root and start spreading through the body and trying to take over the system of the victim. Over the next two months, the victim will experience ranges of terrible pain, nausea, fatigue and fever as they slowly become an ageless humanoid female. Eventually the parasite completely replaces most of the victim's nervous system and also devours their life-force, making it almost impossible for them to use any psychic abilities that they may have had before hand. As such, dryads are treated with a combination of pity and caution. It is known that new dryad trees grow out of dead dryads or oreads, so some people worry that the condition is contagious (of course, most people know it isn't and dryads are both very beautiful and perceived to be defenseless). While some would desire the immortality, few psychics want to lose their abilities to gain the immortality. Dryads will eventually advance to the ideal age for motherhood for their particular species.
Oreads are people that have eaten a dryad vine and did not successfully defeat the parasite but also was not fully transformed into a dryad. They remain the species that they were before, but are now locked at their current age and can only die by violence or disease. They can also learn to feed the parasite and use it as a spare source of Life-Force, making them unusually effective psychics. But the number of people that are cured of the infection or die both outnumber oreads several times over.
Fountains of Youth, Blood Bathers, Peach Trees of Immortality and so on.
There are a number of other methods of achieving immortality but they are generally well-protected by the people that achieved them. Or else they are not aware of how they acquired their immortality. This is where the legend of the fountain of youth came from as at least one incidental immortal has claimed that it was such a supernatural location that made them what they were. Likewise, it is possible that "peaches of immortality" are god-designed plants similar to dryad fruit.
Some incidental immortals use very horrible methods to achieve. There have been shapers and magicians who have both found ways to rip Life-Force from one target and use it to reinforce their own bodies. Some have moved to replace failing organs to keep up their failing bodies. Unfortunately, there are few enough immortals that identifying the manner of how an immortal acquires their ageless nature is difficult. So until they're well known, or they're easily recognized (like dryads) immortals are treated with caution.
Every time a kitsune acquires a tail, their potential life-span grows greater. Eight-tailed kitsune have died of old-age, but nine-tailed kitsune never have.
Immortal RacesUnlike incidental immortals, Demons and Gods are born with a body that will only die to violence. accident or disease. The secret of their immortality is partially evolution and partially due to artifice. The original species that produced the group that would become Demons evolved a psychic Talent that seemed to be a sort of unstable communal mind link and an instinctual ability to invent "things". When they came up with a process to stabilize the mind link without any member of the communal mindscape losing their personality, the resultant stabilization somehow came with immortality. The Gods later developed a similar evolution and stole the secret of stabilizing it from the Demons (though neither species would be known by those words for millions of years later).
The primary theory is that Demons and Gods maintain their physical body via unconscious or subconscious processes. Before they stabilized the mindlink their "understanding" overwhelmed them with sensory overload eventually duplicating aging as distractions caused them to develop cancers or the like. Once the mindlink was stabilized, they had multiple minds capable of maintaining their bodies with minimal loss of processing power resulting in immortality.
Gods and Demons are recognizable by blue and red facial marks (respectively), which are difficult to conceal. Make-up has a tendency to dry out and flake off around the marks, shapeshifting can't erase them and illusions hiding the marks disrupt them. Though with a concentrated effort a Demon or God can maintain a concealment. However, tattoos and even facial tattoos are common enough that most people dismiss the marks as just some cultural thing.