Children of the Echidna are, inter alia, the Cerberus, the Hydra, and Gorgons, though sources vary.
Some myths say she is immortal while others say she was killed in her sleep by Argus Panoptes, the hundred-eyed giant who served Hera. Her mate Typhon challenged Zeus and was thrown directly into Tartarus by him.
The Echidna is described as half beautiful woman, half fearsome snake, either from the waist ("snake-legged") or from the head down.
In one version of the lore, her snake tail is said to eat raw flesh, suggesting the tail actually ends in a snake head.