Telegonus ("born afar") is the youngest son of Circe and Odysseus — not the Egyptian king who wed Io, nor the Thracian son of Proteus slain by Heracles. Grown to manhood, he sails in search of his father, lands unknowing on Ithaca, and accidentally kills Odysseus with a stingray-spined spear. Later tradition has him marry Penelope and found Tusculum; the lost epic Telegony and Sophocles' Odysseus Acanthoplex told the recognition-and-killing tale.
Adapted from Wikipedia, "Telegonus (son of Odysseus)" · CC BY-SA 4.0
I.Homonyms
Greek myth knows several Telegoni. Apollodorus's Egyptian Telegonus is sometimes husband of Io; another Telegonus, Thracian son of Proteus and Torone, dies wrestling Heracles. Hesiod also mentions a Telegonus who rules Tyrsenians in the holy islands. This entry is the Circe–Odysseus son of the Telegony cycle.
II.Death of Odysseus
When Telegonus came of age, Circe sent him to find Odysseus, who had by then returned to Ithaca. Shipwrecked by a storm, he mistook the island for Corcyra and, hungry, began to plunder. Odysseus and Telemachus defended the land; in the mêlée Telegonus unwittingly killed his father with a lance tipped with the venomous spine of a stingray.
Apollodorus's Epitome agrees on the sting-ray spear. Aftermaths vary: Telemachus may marry Circe while Telegonus takes Penelope, becoming father of Italus; a later strand has Circe resurrect Odysseus after the killing.
III.Epic, tragedy, and Italy
The story was told in the Telegony, a sequel to the Odyssey attributed to Eugamon of Cyrene and known chiefly from summaries. In Sophocles' lost Odysseus Acanthoplex an oracle dooms Odysseus to die by his son's hand; he banishes Telemachus, then rushes out against the unrecognized Telegonus and falls — a pattern often compared to Oedipus.
Italic and Roman myth made Telegonus founder of Tusculum southeast of Rome, and sometimes of Praeneste (Palestrina). Roman poets regularly called Tusculum the "walls of Telegonus" or "Circaean walls."