Pandora's box

[Tina]

According to Greek legend, the first woman, Pandora, was actually sent as a curse to Zues men (See, you knew it was true, guys) and was given a present upon her marriage. The present was a box that she was told never to open. Needless to say her curiosity got the better of her (like eating forbidden fruit) and she unleashed eight demons unto the world. The first seven being the seven deadly sins, and the last, which she managed to capture, was hope.
Today, much like christianitys idea of biting forbidden fruit, opening pandoras box refers to getting into a situation over which one has very little control over.