Scylla

In Greek mythology, Scylla, reflecting ) is obsolete.}} ( ; |Skýlla}}, ) is a legendary, man-eating monster who lives on one side of a narrow channel of water, opposite her counterpart, the sea-swallowing monster Charybdis. The two sides of the strait are within an arrow's range of each other—so close that sailors attempting to avoid the whirlpools of Charybdis would pass dangerously close to Scylla and vice versa.

Scylla is first attested in Homer's ''Odyssey'', where Odysseus and his crew encounter her and Charybdis on their travels. Later myth provides an origin story as a beautiful nymph who gets turned into a monster.

Book Three of Virgil's ''Aeneid'' associates the strait where Scylla dwells with the Strait of Messina between Calabria, a region of Southern Italy, and Sicily. The coastal town of Scilla in Calabria takes its name from the mythological figure of Scylla and it is said to be the home of the nymph.

The idiom "between Scylla and Charybdis" has come to mean being forced to choose between two similarly undesirable or risky outcomes, similar to "between a rock and a hard place". Provided by Wikipedia