Hanner Sidhe development history

Here, by using the archived forums, I recall the history of the half-elf as a changed being rather than as an offspring of a human and elf.
In September 2002, Birthright-l member Peter Lubke asked:

"Seriously. What`s a half-elf? a half-human? I can?t see that they should be accepted as a RACE apart.?

Ryan Caveney, who has a significant interest in elves and is widely read in the literature of elves, replied:

?The real story is that "half-elves" are actually a different species of being from either elves or humans, who were originally created by the elves (and dragons?), as a sort of servitor race and experiment in understanding the psychodynamics of mortals. [?] Most humans who think they?ve met elves have in fact only met half-elves, working as the public faces of their masters, getting their hands dirty dealing with the filthy, verminous humans. If they?d met real, full elves, they?d be much more frightened."

Peter then responded by introducing a mechanism for how one might have half-elves without sex:

"Elves could have the power/ability/natural reproductive system of quickening a child when great love or great need is present - such a magical union need not be a blending of two species at all. Given the "elves are creatures of starlight and pixie dust" (whether this is literal or not is unimportant - it`s meant as a description of the wide gap between elves and whatever) - I think that for Cerilia, it will be my choice."

And so we have the core notion of a half elf as something crafted, not born. Crafted by elves in a magical process, perhaps similar to how they reproduce themselves.
Peter then followed with another critical idea on aging:

"What if immortality is related to the Sidhelien life-style (good clean living caring for nature, nothing bad in your body kind of thing)? Then technically their bodies simply don`t age. In such cases a half-elf raised with elves would be similarly influenced. Violence and adventuring outside will slowly age the character - even an elf character - although returning to the forest homes can return the character to a state of [ever-young] statsis."

Ryan was taken with this concepts and embraced them:

"You may even convert me -- this sort of natural ability to one-off for highly personal reasons does seem a lot more consistent with the setting than the sci-fi cliche "vat grown warrior servant race" that previously shaded my interpretation of Cerilian half-elves. One other aspect of my version of half-elves that I don`t recall if I`ve mentioned previously is that there is a difficult and obscure but still occasionally practiced ritual to turn humans (and possibly, but not necessarily, elves) into half-elves (but not, I think, vice-versa). This is an interpretation of the ancient myths about people who spend a night in fairyland and return to find that decades or centuries have passed; it also works well with your idea of "lifestyle immortality" -- humans turned into half-elves this way can live forever if they stay in fairyland, but grow old and die if they leave. Literary sources for this idea range from an alteration of Earendil's choice in Tolkien, to Sinclair and Delenn in Babylon 5, to the AD&D 2e FR "Cormanthyr" supplement, and IMO to veiled plot hooks in some of the BR materials. There are a couple of ostensibly human wizards in Anuire and Khinasi (ed. refering to Torele Anviras and Adara bint Reshoud) who are rumored to be much older than they look, and have once disappeared to parts unknown for a long time, after which they came back both more powerful and different somehow. IMC, they went to the ancient Sidhelien forests and were turned into half-elves. Their reasons for doing it are clear: longer life, a chance to study with the best wizards on the planet, and IMC since bloodline and elven ancestry each separately enable wizardry, having both makes you even better at it. What the elves get out of it is less clear; presumably various forms of service are required as payment, and powerful geases are placed on the recipient to make sure that the powerup works to advance rather than hinder the Sidhelien cause."

And so it is presented in full. Characters who disappear into the Sidhelien forests only to be turned into half-elves, returning much later, appearing much younger and more powerful. Servants to the Sidelien cause.
Ryan then comments on some related elements, regarding how leaving the old forests will age elves and half-elves:

"I actually use a variation on this IMC, but it`s not so much "lifestyle" as it is magical biology. That is, IMC, the way Sidhelien immortality operates is that they draw sustenance directly from ambient magical energy: that is, mebhaighl. My Sidhelien can only really live comfortably in a province with a source potential of at least six. In provinces with potential nine, they have stat and speed bonuses, and don`t actually need to eat at all unless they want to. Around source potential 3, they become susceptible to disease, need to sleep, and have to eat about twice as much as a human of the same mass. Below that, they have stat and speed penalties, tire easily, need to eat much more than humans do to maintain health, and actually begin to age. Trapped in a province with source potential zero, an elf will die of magical starvation in about a week. All these bad effects can be halted or reversed by going back into a province with a sufficiently high source potential and staying there long enough."

Kenneth Gauck began to combine the whole thing and historicize it:

I wonder if the Sidhe didn`t initially respond to human arrival with a hope of just converting the humans into half-elves. As time went on the humans appeared to be too many, not particularly interested in such a conversion, and ultimately destroyed the sylvan forests. After a Sidhe moment to reconsider, some of them adopted the opposite approach of the gheallie Sidhe. They decided to pick specific humans of power and promise and apply the mystical processes to them. This hope that humans can ultimately be converted to a Sidhelien life-style and even better a half-elf existence remains. The elves have taken the long view.

John Machin refined the issue of health and aging:

Aging never really came up as a major motif when we were playing BR using (A)D&D rules. However when I adapted Ars Magica this changed rapidly. Ageing is highly important in ArM (where characters can often die from disability brought on by age). The numbers and the principle of flexibility I mentioned earlier arose from the needs of using this sort of system to portray sidhe and half-sidhe. I personally consider half-sidhe longevity to be dependent upon the individual?s outlook and their lifestyle. Living a more "human" existence will mean that a half-sidhe has a somewhat shorter lifespan, whereas living a "sidhe" lifestyle could mean that the half-sidhe may last millennia before succumbing to age, if at all.

From there discussion explored Sidhe reincarnation and other issues, such as "the plan", but a new notion of what a half-elf was, had been thoroughly developed.