Aethra (Greek mythology)
Mother of Theseus
Aethra was a daughter of King Pittheus of Troezen and the mother of Theseus (his father was the king Aegeus of Athens, or in some versions, Poseidon). Aegeus went to Troezen, a city southwest of Athens that had as its patrons Athena and Poseidon, where Pittheus got Aegeus drunk on unmixed wine and put him to bed with his daughter. Following the instructions of Athena in a dream, she left the sleeping Aegeus and waded across to the island of Sphairia that lay close to Troezen's shore. There she poured a libation to Sphairos, Pelops' charioteer, and was possessed by Poseidon in the night. When she was thus doubly pregnant, Aegeas decided to go back to Athens. Before leaving, he covered his sandals, shield and sword under a huge rock, that served as a primitive altar to Strong Zeus, and told her that when their son would grow up, he should move the rock and bring his weapons back. Aethra did as she was told, and Theseus, recovering the weapons that were his birthright, grew to be a great hero, killing the Minotaur, among other adventures.
Later, when Theseus kidnapped Helen, he gave her to Aethra for safekeeping. Helen's brothers, the Dioscuri, took Helen back and kidnapped Aethra in revenge. She went to Troy with Helen and remained there until found by her grandson, Acamas, during the fall of the city.
With significant alterations to the character, a version of this Aethra appears (as "Aithra"), a sorceress and concubine of Poseidon, in Richard Strauss's famous opera Die ägyptische Helena (The Egyptian Helen).
Aethra is also the name of one of the Oceanids, the 3000 daughters of Oceanus and Tethys. She is sometimes called the wife of Atlas and mother of the Pleiades and the Hyades (more usually the offspring of Pleione).