What modern expression describes an action that releases many unexpected problems, like Pandora’s jar?

The modern expression “opening Pandora’s box” describes an action that releases many unexpected problems. It comes from the Greek myth in which Pandora opens a jar and troubles spread into the human world.

The expression became established in English and other languages through later retellings and translations. The ancient Greek source describes a pithos, a large jar, but the Latin translation associated with Erasmus used pyxis, a box or container. That translation helped produce the familiar phrase and the standard visual image of a box.

The idiom is generally used figuratively for a decision or discovery that creates consequences difficult to control. It is not limited to mythology or literature. “Opening Pandora’s box” differs from “crossing the Rubicon,” which refers to an irreversible decision, and from “opening a can of worms,” a separate modern idiom with a similar sense of complications.