Sciron (also Sceiron, Skeirôn, Scyron) is the Corinthian brigand of the Scironian Rocks on the Megarian side of the Isthmus — one of the malefactors Theseus kills on the road from Troezen to Athens. He forced travellers to wash his feet at the cliff's edge, then kicked them into the sea for a giant turtle to devour; Theseus cast him down by the same death. Megarian tradition instead made him a warlord and chastiser of robbers, grandfather of Peleus and Telamon through Endeïs — a figure the atlas keeps distinct from this Isthmus robber where the genealogies diverge.
Adapted from Wikipedia, "Sciron" · CC BY-SA 4.0
I.The robber of the rocks
An Isthmian outlaw, Sciron haunted the frontier between Attica and Megaris on the Saronic coast. Sitting by the sea he compelled passers-by to wash his feet at a precipitous place; as they knelt he kicked them over the cliff, where a monstrous turtle swam under the rocks — or the bodies rolled down to a place called Chelone ("tortoise").
As his fourth labour on the road, Theseus slew him in the same fashion, pushing him from the cliff or seizing him by the feet and casting him into the sea. Pausanias notes a burnt-clay pediment group at Athens's Royal Stoa showing Theseus throwing Sciron into the sea; Ovid ties the cliff-name itself to the man.
II.Parentage
Apollodorus makes him son of Pelops (and possibly Hippodameia) or of Poseidon. Other sources name Canethus and Henioche (a daughter of Pittheus), making him Theseus's cousin, or call him son of Pylas of Megara and thus great-grandson of Lelex. Through a daughter Endeïs — by Pandion's daughter or by Chariclo daughter of Cychreus — some genealogies make him grandfather of Telamon and Peleus; a son Alycus is said to have fallen when Theseus kidnapped Helen.
III.Megarian warlord and Isthmian Games
Plutarch records the Megarian claim that Sciron was no robber but a chastiser of robbers, kinsman of Aeacus and grandfather of Peleus and Telamon — unlikely, they argued, to ally with basest men. In Pausanias's Megarian politics he disputes the throne with Nisus after Pandion's line; Aeacus arbitrates, leaving Nisus the kingship and Sciron the war command, sealed by Endeïs's marriage to Aeacus.
One version has Theseus found the Isthmian Games to honour Sciron and expiate the murder because of their kinship; others, Plutarch notes, give that honour to Sinis, another bandit Theseus killed. The atlas character sciron-isthmus is the foot-washing brigand of the Theseus road, kept apart from the Aeginetan grandfather of the Aeacids where those strands conflict.