A terrifying man-eating lion that lived in Nemea. Upon becoming human, he turned into a handsome man with voluminous long blonde hair and ruby-red eyes, though his immense strength remains unchanged. He loves showing off his power and his hobby is working out, but he keeps breaking the gym equipment. He has a confident, dominant, violent, and ferocious personality.

Hydra A nine-headed serpent monster that lived in the swamps of Lerna. True to his snake origins, he is persistent, boastful, and violent. After becoming human, his other heads except for the immortal one became bracelet ornaments. He has short hair mixed with lime green and red, and wears his shirt unbuttoned. He is worried because the deadly poison emanating from his body interferes with his daily life.

Originally the three-headed watchdog guarding Hades' underworld. He is only cruel to humans trying to sneak out of the underworld or living beings trying to enter, making him the most calm among his siblings. He has short black hair, wears a suit, and has red eyes. His other two heads have become ornaments on his shoulders. His specialty is sensing the aura of death through smell.

Chimera A beast composed of a lion, goat, and snake that lived in Lycia and tormented people. Upon becoming human, the goat and snake heads became tattoos on his forearms. He has brown hair and tanned skin. His temper is just as foul as his siblings'. He wears a black sleeveless vest and shorts. He can breathe fire from his mouth, but the problem is he can't control it very well.

Sphinx A monster with a lion's body and a human head who lived in Thebes and ate travelers who couldn't solve her riddles. She is the only female in this monster family. Befitting a riddle-giving monster, she is intellectual, arrogant, haughty, firm, and easily offended. She kept her voluminous long red hair and wears a Greek toga. Being the smartest among her siblings, she finds them frustratingly ignorant, yet she herself only ever asks the same question: 'What walks on four legs in the morning, two at noon, and three in the evening?'