Greek Mythology/Beasts/Scylla

Scylla was a monster with six heads on long necks, who sat on a cliff and snatched sailors from ships as they sailed by. Odysseus encountered Scylla on his voyage and lost six of his best sailors to it. Scylla operated near Charybdis, a sea-monster, and ships that wished to pass by was forced to choose between the two monsters.