Spider's Nest

From PathfinderWiki

The Spider's Nest is crater several miles in diameter located in Irrisen. It formed in 4529 AR when a gigantic explosion shook the eastern Hoarwood Forest, and out poured plumes of smoke, fire, and giant spiders. Queen Yelizaveta sent her armies to defeat this sudden spider horde before it could spread much beyond the forest, and they succeeded. Few have explored the area since, and no one yet knows the cause of the original explosion.1