Long ago, contemporary to the ancient, long turned to dust Aviontix, were the Sarethians. Their deities were serpentine in nature, as the Aviontix were avian. There was a great upheaval in their culture according to the few ancient records that have been translated. The young fought the old for control of their destiny or some such. The story has fallen into myth, being used for moral messages of respect your elders and follow tradition (after all, if the young had done that, their culture would not of ended otherwise). Very little survives of their culture except for a few scrolls of exceptional poetry and magical theories, and their entire legal system (which was draconic at best - mercy not being a big quality for the Sarethians). Well, all that is left that anyone really knows of…
The Order of Serpenthia has been a social group that uses Sarethian motiffs. It has been a gentleman’s/ noble order for many centuries. It seems to center around supporting traditional values and forms, as well as respect for Elders. Every now and again, people say that there is a mystery cult within the group, that harkens back to the times soon after the loss of the Sarethian Kingdom. There are even darker rumors of strange magics and worshiping of Old Gods going on. Most of that is just mud slinging by people who were not allowed to join the group.
It is a secret society of some antiquity. Some of its members are part of that antiquity. You see, some of the Saretheans achieve extreme longevity, if not immortality. The altercation between the younger and older near immortals tore their society apart, especially since there were no children except those they “adopted” (kidnapped).
The society trades ancient techniques for longevity and vitality for temporal power and covert secrecy. The few remaining Saretheans and a few others of extreme age, form a central council. They direct members and those “in the wings” to protect their secrets, arrange new papers and identities for their elder members, places for more elderly appearing members to live comfortably (who look like living mummies), and manipulating certain current events to support the society AND its members.
The most central technique they teach is “Binding the Life Coil”. This quasi-mystical technique rediscovered to prolong one’s life at the expense of one reproductive ability. It is a simple magikal technique that anyone can learn (a skill or feat), but the members teach only a few pieces of it to their “in the wings” members at a time… teasing them with immortality. (The promise of near immortality or a lifespan of a thousand years or more makes everyone want to learn it.) This technique has a price though, the amount of immortality is in direct response to the strength of ones reproductive spirit. Those that have never breed will live longer than those that have.
Note: The use of the technique makes conception difficult, if not impossible. So you trade the future of your society for the chance for you to see much of that future. This technique was truly the downfall of their society.