Homer's Iliad gives the earliest surviving description of the Chimaera and keeps it simple: a thing of immortal make, not human, lion in front, serpent behind, and goat in the middle, breathing out the fierce might of blazing fire. Later Greek vase painting and sculpture, and Hesiod's Theogony after Homer, settle the composite into the form that becomes standard, a lion's body and head, a second head belonging to a goat rising from the middle of its back, and a tail that ends in a live, striking serpent, so that three animal heads effectively sit on one body. She is counted among the monstrous children of Typhon and Echidna, siblings to Cerberus, the Lernaean Hydra and the Sphinx, a family of hybrid terrors that heroic myth exists largely to clear from the world one at a time.
Fire is her signature weapon as much as any of her three animal parts, breathed from at least the lion's head and sometimes described as issuing from all three, and it is specifically her fire that makes her impossible to approach safely on the ground, which is why Bellerophon's aerial attack from Pegasus's back becomes the only way ancient tellers imagine defeating her.