Have you guys heard the term “harvestmen”?
“Harvestman” seems to be a folk name for what I always called a daddy long-legs: a scarier, more awesome name, I think. It’s ominous even before you know that harvestmen are giant freaky spider-things.
The name “harvestmen” practically comes with a built-in adventure. Imagine a village where people keep on warning the PCs about the coming of the Harvestmen. Maybe no one in the village is older than 30. Then these leggy spider guys finally show up. They’re harvesting the older villagers, including any older PCs.
Real harvestmen have a stink attack that they use when threatened, and their legs continue to twitch after they are severed, which in D&D terms means, I think, that severed legs attack independently.
By the way, harvestmen reproduce sexually. Maybe only female villagers are harvested. Creepy!