Cancer (the Crab)

In the Heracles/Hercules tradition the creature called the Crab is sent (by Hera, in the accounts cited) to oppose the hero during his combat with the Lernaean Hydra. The crab attacks or distracts Heracles and is crushed by him; in the mythic-astronomical afterlife of such tales the creature is then placed among the stars as the constellation Cancer, explaining the origin of that zodiacal figure.

Sources describe the entity simply as a crab or, in some graphic uranographic depictions, as a crayfish. In narrative contexts it is characterized as a "giant crab" (the scaling befitting a mythic antagonist). Uranographia (Johann Elert Bode) is cited as an example where Cancer is depicted as a crayfish; classical references otherwise refer to it as the Crab without elaborate supernatural anatomical detail.

Narrative sources attribute no special magical powers beyond its role as an oppositional crustacean in the Heracles cycle; its physical effectiveness in the story is its assault on the hero and consequent crushing by Heracles. Its principal cultural "ability" is etiological: by virtue of the myth it is memorialized among the stars as the constellation Cancer, a fixed member of the Zodiac. The supplied materials do not describe ongoing interactions with humans or persistent supernatural agency beyond this memorialization.