“Since the vile Plante’s Deceased Hoste is not technically a Part of its Anatomy, any attemptes to Kill the Monster using regular methods is likely to prove Futile, especially that of Beheading the Creature. It seems to regarde its Head as a most Unnecessary part of its Composition, and thus as it moves its Head exhibits a frightening lacke of Expression, and lolls in a way most Unpleasant to observe.”
Long sieges can be a trial for both sides. For the beseiged especially, finite ammunition supplies always pose a problem - except when the ammunition can reproduce…
"Binding the Life Coil" is an ancient 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). 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. 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.