The Spider Invasion

From the introduction:

Long before the strange things started to happen in town an explorer in the Amazonas came across an old abandoned temple. The explorer then brought with him a number of objects that he thought he could sell and become rich. One of those objects was an obsidian plaque, about 30 cm in diameter, and with strange inscriptions, and the image of a spider inlaid with gold. The plaque then ended up being sold to a collector, and many years later one of his adult grandchildren was going though an old storage-crate and accidently dropped the plaque, so it broke in half. That released the spider demon, who managed to scatter away and hide in a corner in the large shed that was used as storage space. There it laid its eggs.