Sinis (also Pityocamptes, "the Pine-bender") is the Isthmian bandit Theseus kills second on the road from Troezen to Athens. He forced travellers to help bend pine trees, then released them so the springing trunks catapulted or tore his victims apart; Theseus repaid him with the same death. He is father of Perigune, by whom Theseus later fathered Melanippus — kept distinct in the atlas from other Isthmian malefactors such as Sciron.
Adapted from Wikipedia, "Sinis (mythology)" · CC BY-SA 4.0
I.Family
Pseudo-Apollodorus makes Sinis son of Polypemon and Sylea, daughter of Corinthus; other accounts name Canethus and Henioche. Bacchylides gives him Poseidon as father. He was the father of Perigune.
After Theseus killed him, the hero lay with Perigune, who bore Melanippus; she was later given to Deioneus of Oechalia.
II.The Pine-bender
An Isthmian outlaw, Sinis compelled travellers to help him bend pine trees to the ground, then unexpectedly let go so the springing trunks hurled his victims through the air. Alternative tellings have him bind a victim between two bent pines that, when released, tore the body apart. From this cruelty he was called Pityocamptes.
He was the second bandit slain by Theseus on the road from Troezen to Athens, killed in the same fashion he had used on others. Plutarch records that some credited Theseus with founding the Isthmian Games to honour Sinis (or Sciron) and expiate the kinship-stained murder — a tradition the atlas keeps as prose beside the robber of the pines.