Ancient Greek Mythology, Religion, Art
Theseus was one of the great legendary kings of Athens who embodied many of the qualities Athenians eventually considered necessary for their own citizenship. The Temple of Hephaestus in Athens has, in the past, been called the Thession in the belief that it had been dedicated to him and, perhaps, had held his bones. Veneration of him does not, however, appear to pre-date the 6th century BCE.
Like other Greek heroes Theseus was the son of a mortal (Aethra) and an immortal (Olympian god Poseidon). Aethra's husband, king Aegus, left her in Troizen and told her that is she bore a son he should not follow after him until he was able to lift a large rock, taking the sandals and sword hidden underneath.
At 16 Theseus learned of his parentage, lifted the rock, and proceeded to Athens with the sandals and sword. Theseus had many adventures and achieved many great deeds - for example, inventing unarmed combat techniques. His greatest feat, however, was the killing of the Minotaur in Crete. Every 9 years Athens was forced to send 7 young men and 7 young women as sacrifices to the Minotaur, child of Pasiphae, king Minos' wife, and a bull.
Theseus volunteered to go and, once there, slays the Minotaur with the help of Minos' daughter Ariadne (who, in turn, had been helped by Daedelus, an Athenian craftsman who became famous for building wings so that he and his son Icarus could escape Crete). Theseus, then, was responsible for freeing Athens from the bondage of king Minos, allowing the citizens to live in greater peace and security - exactly the sort of political role required of heroes as religious figures.
Bound to the city of their origin, Greek heroes were expected to continue helping the citizens of that city - and Theseus is believed to have done just that According to legends Theseus' spirit appeared to the Athenian warriors at Marathon, lifting their morale and thereby helping them to go on and defeat the Persians.
Theseus would not have appeared to any other group of soldiers because, unlike the gods, he belonged to Athenian history, the Athenian community, and Athenian religion. He was both a symbol and a talisman: a symbol of where the Athenians had come from and a talisman against the dangers they faced in battle. If he could do so many great things like slay the Minotaur, then they could do great things as well.
As noted above, veneration of Theseus isn't observed prior to the 6th century BCE. There were also relatively few sanctuaries dedicated to him in the Attic region. He was, however, honored in various festivals. There was a particular festival, Theseia, dedicated entirely to him and he was brought into other festive events as well.