Once upon a time, Zeus, taking the form of a swan had seduced Leda, the wife of King Tyndareus of Sparta. That same day, Tyndareus also lay with Leda. Subsequently, instead of delivering a baby, Leda laid an egg. From the egg were hatched four babies. First the twin brothers Castor and Polydeuces, also known as the Dioscuri came out. Thereafter, the sisters Clytaemnestra and Helen came out of the egg. Polydeuces and Helen were the immortal children of Zeus, while Castor and Clytaemnestra were the mortal children of Tyndareus. When the children grew up, Tyndareus gave Clytaemnestra in marriage to Tantalus, the son of Broteas. Clytaemnestra begat a child to Tantalus.
Meanwhile, Aegisthus, the son of Thyestes, had killed his uncle King Atreus of Mycenae and subsequently, Thyestes, became the king of Mycenae. Agamemnon and Menelaus, the sons of Atreus also known as the Atrides, were exiled from Mycenae. In exile, the Atrides resided with King Polyphides of Sicyon for some time and later, stayed with King Oeneus of Calydon. Soon, they sought the help of King Tyndareus of Sparta and launched an attack on Mycenae. Thyestes fled away to the Cythera island and the Atrides seized power of Mycenae. Agamemnon became the King of Mycenae.
Agamemnon desired Clytaemnestra. He killed Tantalus, snatched Clytaemnestra’s babe from her breast, and killed the babe by dashing the babe against a stone wall. The Dioscuri came to avenge their sister, but Agamemnon as a suppliant, knelt before Tyndareus and prayed for mercy. Tyndareus rescued Agamemnon and gave Clytaemnestra in marriage to Agamemnon. This marriage united the kingdoms of Mycenae and Sparta.
Later, Tyndareus married his extraordinarily beautiful stepdaughter Helen, to Menelaus, the brother of Agamemnon. After the Dioscuri became gods, Tyndareus gave the throne of Sparta to his son-in-law Menelaus.
Excerpt from the book “Once Upon A Time-II: 150 Greek Mythology Stories” by Rajen Jani