You can hear the song from miles away. The song is enchanting in a mild way. Even the plants sing this haunting tune all day. This gives you fair warning to be ready to dance to a different tune. You are leaving your country and entering theirs.
This relic, while of little value against the living, is a formidable tool against the beasts from beyond.
The D’athri took to space in such a way to make Terrans look "gun shy". They can be found in small numbers in and around every space port in Known Space.
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.