In Mark Waid’s “Irredeemable” Scylla and Charybdis are a superhero duo with “twin powers” much like Hawk and Dove from DC. Their names however, are taken from a Greek Mythology.
According to Homer, they were mythical sea monsters. Later Greek tradition sited them on opposite sides of the Strait of Messina between Sicily and the Italian mainland. Scylla was rationalized as a rock shoal (described as a six-headed sea monster) on the Italian side of the strait and Charybdis was a whirlpool off the coast of Sicily. They were located close enough to each other that they posed an inescapable threat to passing sailors.
What modern phrase could be attributed to them?