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.
Faerie foods with unusual effects. Like faerie sausages that turn the eaters into wiener dogs, faerie wines that make the drinker whiny, etc. There's a table in Palladium Fantasy RPG which has a table of ideas.