Far, far to the south, where east and west meet and become north, there is a valley, carven not by the slow slide of the world's rocky skin over her firey heart, but rather the wind and water have carven it, deep and narrow, folding away from the sun. Here, at its deepest depths, the Light never reaches. Here, at the top of the bottom of the world, lies the place which Shadow and Darkness have dedicated to themselves.
A secret MLM (pyramid) company that offers eternal life, but in fact it transfers the life forces of its members to those position "above". If you get high enough, (meaning you get enough new members) you start to enjoy the benefits. Maybe a willing sacrifice is much more effective for the transfer. But no one says, that a suddenly unwilling member, threatening to tell the authorities, may not loose it involuntarily... thus start people to vanish, and aged corpses are deposited somewhere safe.