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

“Opening Pandora’s box” describes an action that creates many unexpected problems.

The expression comes from the later popular form of the Greek myth. Pandora opens a sealed container, releasing troubles into the world. In modern English, the phrase is used figuratively when one decision or investigation begins a chain of complications that is difficult to reverse.

The wording is based on the idea of Pandora’s box, although Hesiod’s original account describes a jar. The box image became established through translation and later literary tradition, then spread into everyday journalism, politics, business, and popular culture.

The phrase does not literally require a forbidden object or a curious woman. It can describe any apparently small action with broad, unintended consequences. This differs from “Achilles’ heel,” which means a vulnerable weakness, and “the Midas touch,” which refers to an ability to make things successful or profitable.