For 10 points, identify this type of creature, examples of which include the Hydra and the guardian of the Hesperides, Ladon.
When one of these creatures was ravaging Thespiai, Menostratus killed it by feeding himself to it while wearing spiky armor. Cadmus killed one of these in the spring of Ismene, and one of these named Delphyne guards the sinews of Zeus. Medea's flying chariot was driven by two of these creatures, and (*) one of these creatures was killed during Heracles' eleventh labor. The drugging of this type of creature allowed Jason and Medea to escape with the golden fleece. For 10 points, identify this type of creature, examples of which include the Hydra and the guardian of the Hesperides, Ladon. 
When one of these creatures was ravaging Thespiai, Menostratus killed it by feeding himself to it while wearing spiky armor.
Dragons [prompt on "serpent" or "snake"]