And so the old story goes that Pandora's curiosity got the better of her. When she opened the box given to her by Zeus, all the evils of mankind flooded out upon the world. And thus ended a long period of boredom where everyone was nice to each other.
At least Pandora had an excuse: a lack of hindsight. The hero of Legendary really should have known better. By opening the proverbial box he unwittingly releases a horde of mythological beasts into New York City, everything from minotaurs to giant salamanders. Seriously, what did he think was going to happen?