What is the common English expression for releasing a chain of unforeseen troubles by opening Pandora’s container?

The common English expression is “opening Pandora’s box.” It describes starting a process that releases many unexpected problems or harmful consequences.

The expression comes from later retellings of the Greek myth in which Pandora opens a container and the evils inside spread throughout the human world. The ancient Greek account describes a jar, but the English idiom uses “box” because of a long-established translation tradition.

In ordinary English, the phrase is usually metaphorical. Someone may “open Pandora’s box” by introducing a complicated policy, revealing hidden information, or beginning an investigation whose consequences multiply. The expression does not normally refer to a literal container.

The idiom is related to, but not identical with, other classical expressions such as “opening the floodgates.” Its distinctive meaning is the release of numerous problems from one apparently contained source. Hope’s presence in the original myth is also often omitted from modern idiomatic use.