Re: "Kryptonites" => evolutionary variation & crisis
I forget if I even replied to this before or not, seeing as I haven't (apparently) checked my inbox in ages....
The main Otherkin-correlated physical allergies/weaknesses that can be considered genetic, I think, are dietary compulsions & preferences, light sensitivity and skin/contact allergies, like vampires' and (RL) trolls' common sensitivity to sunlight, and the allergy to iron that some fae claim (which I think is related to potential hyperoxidation of cells due to lingering genetic instability).
Other ailments and commonly-termed "disorders" that I've noticed a fair amount within the demographic (though I do not see them as definite indicators on their own, of course) are asthma, bipolarity, depression, dyslexia, autism/Aspergers, the whole range of atypical gender identities, sexual queerness and kinks/BDSM in general, plus occasional (and thankfully rare in my acquaintance) full-blown psychotic disorders. I think that some of these are related to our kin-natures and the accumulated patterns & flexible changes of past lives running into the rigidity of a single life, some of them are defenses/reactions against dealing with our natures, gifts and past/present traumas, and some of them are what happens when a person does not know how to deal well with the realities that they perceive around and within themselves. And that's not even counting the active manipulation/evocation of fear that is a frequently-reported "testing" among the psychically-gifted who can perceive demonic and spiritual activity.
There are a variety of other ways that we can get sensitized or vulnerable to things when it is not genetically in our pattern already -- some of it probably has to do with psychic attention, how we spend our energies and where our anxieties and stresses are located (Reiki is a good system for addressing and understanding this, as is EFT) -- and some of it is a general matter of (fairly often) being sensitive to things that are oversynthesized or overused in modern life (common food additives & preservatives, household chemicals, noise, etc.), and needing to control exposure and bring our physiological systems back into balance, through fundamental things like solid nutrition that supports one's kintype needs, physical activity and contact with nature, music, other people, or whatever feeds one's energy best (I don't consider energy-feeding to be a solely vampiric activity atall).
One profile that often applies to otherkin is the concept of "shaman sickness", in all of its meanings -- there can be a lot of various physical illness associated w/ denying and resisting one's nature (which one either loses w/ self-acceptance or learns how to treat), as well as increased physical sensitivities later on due to having a great deal of energy and attention placed in astral realms, whether w/ traveling, determined memory-delving or basically anything but one's physical grounding....effects of the latter phase can range from a headache or hangover syndrome to drastically-reduced immunity. So, balance is kinda important in that, and respect for the flesh, so to speak...
Genetically overall, one thing that I tend to believe regarding otherkin is that our genetic diversity is part of an evolutionary strategy -- parallel though not neces. identical with the purposes of reincarnation and pastlife resurgence -- that tends to occur, so far as I have read, when a species in reaching a crisis and needs to find as many different ways to try evolving as quickly as possible. I believe it's a drive towards potential (re)speciation, which is something that generally tends to happen within isolated/divided populations of animals, often after a drastic reduction in population (a "population bottleneck") -- the combination of population drop and subsequent speciation of the remainder is an extreme case of what is known as a "founder effect" [http://en.wikipedia.org/wiki/Founder_eff
Now....I don't know how many otherkin want to think about themselves as being an active part of evolution -- it all does seem very X-Men, doesn't it, with the "post-human" race and all? Both environmentally and socially, though, it seems to me that the human species may actually be at a point where it is in effect if not in fact isolated, fragmented, and has a confused sense of its size. Conceivably, we seem to have nature trying to "thin the herd" at the same time as we have an unprecedented amount of individual phenotypic variation -- basically, something like putting the respeciation before the population bottleneck, and conceivably to prepare for it, to have as many evolutionary options open as possible.
[Note: I think this is one of the most ambitious theories in the entire area of "otherkin studies"....feel free to think it far-out and crackpot, even though it doesn't even bring up 2012 or Armageddon....]
So, what I tend to think about our weaknesses and kryptonites is that they're things we have to learn to deal with and grow all the stronger for, if we are going to be the individual types of people that are going to survive in an unstable world. The fact that they're considered abnormal and even 'defective' traits in this rather homogenous modern civilized culture doesn't mean that they don't have possible evolutionary advantage in other ways, or that they won't be the tools, along with our accepted gifts and positive genetic strengths and sensitivities, to create new understanding and social systems and ways of thinking altogether. Which is all rather grandiose and utopian, which is why I generally just stick to addressing the immediate present in terms of what we deal with as individuals, especially considering how fractured and factionist the otherkin demographic is at the present time.
Plus, you know, the minute you start talking about there being an innate purpose to anything in existence, someone's usually going to pop outta the woodwork and try to shoot you down with absurdist reductions and Flying Spaghetti Monster baiting....