What is the name of the sea monster who has six dog heads and eats sailors when they pass?

In Greek mythology the name of the Sea monster that has six dog heads and eats sailors as they pass by is the Scylla. The Scylla was said to have lived on one side of the narrow channel of water opposite another monster called the Charybdis.

Sailors trying to pass through he narrow strait that separated the two monsters would often fall victim to one or the other trying the avoid its counterpart. The Scylla made its first appearance in history in Homer’s Odyssey where Odysseus and his crew encounter both the Scylla and the Charybdis. Later on the Scylla was given an origin story as a beautiful nymph that go turned into a monster.