An exception was Heracles, who was accepted in the passage of time among the Twelve Olympians. Such demigods were always mortal, but were preeminent among humans, and some had unusual powers. The veneration of heroes was part of chthonic rites in the religion of Greece. Zeus became the father of many heroes as a result of his dalliances, and after death they were accorded honors, especially among those Greeks who claimed to be their descendants and to have claims on the protection and patronage of a god. Theseus fought to save his homeland, killing the Minotaur to stop the flow of sacrifices that were taken from Athens on a yearly basis to feed the beast. Others, such as Heracles, fought to reclaim lost honor. They would go out of their way to prove their valor, often engaging monsters or beasts far too powerful for any normal human to defeat, for the sole purpose of spreading their name. These hybrids were stronger, braver, and quicker than other mortals, accomplishing super-human feats only possible because of their divine parent. The females were expected to remain loyal to their husbands, while the males were almost expected to take multiple lovers, meaning that far more of the demigods in Greek myths were born on earth to human mothers than on Olympus to divine mothers. Zeus, primarily, and also Poseidon, both had a multitude of affairs with mortal women, with Zeus having to shield them from his wife Hera after she was alerted to the infidelity. The fact that male deities of Greek myth had far more notable children with mortals than the female goddesses can be attributable to the Greek male-dominated society being reflected in their religion.

Thus the heroes have liminal qualities that enable them to have great strength, to cross the threshold between the worlds of the living and the dead yet return safely, and to mediate long after their death between human and divine. This scenario is also occasionally embellished with the theme of double paternity: the hero's mother lying with king and god in the same night (the mother of Theseus, for example) or to be visited secretly by the god (like Danaë, mother of Perseus), and the seed of the two fathers is mixed in her womb.

Part of the dual nature of Greek heroes that gave rise to the modern demigod conception of them is that one parent is a mortal, and another is a god.

Demigod definition