Succubus stones: a powerful succubus sorceress once sought a way to draw more people to her without the use of minions and without having to lift a finger.
The players encounter a room, octagonal in shape. in the center is a great red ruby. upon checking the stone and the surrounding area multiple times, the party, two warriors and a thief, finds nothing odd about the stone or the room, save that there is a large free ruby. As one warrior reaches for it, it begins to produce beautiful and unearthly singing. they are all forced to draw closely around the pedestal. As they get as close as soon as they can possibly get, the song turns into an unearthly wail, paralyzing the players. The succubus then comes to strip the players of their flesh and souls.