What modern idiom describes releasing many unforeseen problems, echoing the Greek myth of Pandora?

“Opening Pandora’s box” is the modern idiom for releasing many unforeseen problems. It comes from the Greek myth in which Pandora opens a vessel and troubles spread into the human world. In current English, the expression usually describes an action whose consequences create a complicated and difficult situation.

The idiom is related to, but not identical with, the ancient story. Hesiod’s original vessel was a pithos, or large jar, and the later box wording developed through translation. The phrase became especially useful because it compresses the myth into a vivid warning about unintended consequences.

“Opening a can of worms” is a similar modern expression, but it is not the Pandora-based idiom. “Crossing the Rubicon” refers to passing an irreversible point, while “meeting one’s Waterloo” means suffering a decisive defeat. These neighboring idioms can sound plausible as answers, but only “opening Pandora’s box” directly names the myth.