The Watcher of the Mists
Goblin Day refers to the events of 4 Rova 4711, in the town of Sandpoint, during that year’s Swallowtail Festival. On that day, several dozen goblins staged a coordinated raid on the town in the midst of the annual holiday. The goblins were terrifying, and tried to burn lots of buildings, but were stopped by the combined forces of the town guard and a band of adventurers that happened to be in town that day.
While the goblin raid was terrifying at the time, only two people were killed by the goblins, and very few were injured. Most people primarily remember the weirdly comic antics of the goblins rather than the terrible destruction they could have caused had not a band of adventurers been there to stop them.