Pelias was king of Iolcus in Greek mythology, son of Poseidon and Tyro, twin brother of Neleus, and the ruler who sent Jason after the Golden Fleece. Having seized power from Jason's father Aeson, he was warned by an oracle to fear a one-sandaled man; when Jason appeared, Pelias dispatched him to Colchis. On Jason's return Medea tricked Pelias's daughters into killing their father in a false rejuvenation rite; his son Acastus then claimed the throne.
Adapted from Wikipedia, "Pelias" · CC BY-SA 4.0
I.Family and early years
Tyro, wife of King Cretheus of Iolcus, loved the river-god Enipeus. Poseidon took Enipeus's form and lay with her; she bore twin sons, Pelias and Neleus. Exposed on a mountain, the boys were raised by a herdsman or maid. Grown, they found Tyro and killed her stepmother Sidero for mistreating her — Pelias slew Sidero even in Hera's temple, earning the goddess's lasting hatred.
Pelias banished Neleus and Pheres, imprisoned Aeson, and sought dominion over Thessaly. Aeson secretly fathered Jason and sent the child to Chiron on Mount Pelion. Pelias's wife is named Anaxibia (daughter of Bias) or Phylomache (daughter of Amphion); his children include Acastus and the daughters collectively called the Peliades — among them Alcestis, Pisidice, Pelopia, and Hippothoe.
II.Quest for the Golden Fleece
An oracle warned Pelias to beware a man wearing one sandal. Years later, at a sacrifice to Poseidon by the sea, Jason lost a sandal in the flooded river Anaurus — in Virgil and Hyginus while helping Hera, disguised as an old woman, across the stream. Announced as the one-sandaled man, he was asked by fearful Pelias what he would do if confronted with his prophesied downfall; Jason answered that he would send that man after the Golden Fleece. Pelias took the advice and set the task.
The fleece hung in a grove of Ares at Colchis, guarded by a sleepless dragon. Jason built the Argo, gathered the Argonauts, and with Medea's help yoked Aeëtes's fire-breathing bulls, sowed the dragon's teeth, and stole the fleece before fleeing with Medea and Absyrtus.
III.Death
In Jason's absence Pelias told Aeson and Promachus that the Argo had sunk; they drank poison, or Pelias killed them outright. When Jason and Medea returned and Pelias still refused the throne, Medea demonstrated a false rejuvenation: she cut up an old ram, boiled it, and produced a live young ram. The Peliades then cut their father to pieces and boiled him, expecting the same miracle; he did not survive.
An alternate version has Medea truly revive Aeson after slitting his throat, then break her promise when Pelias's daughters do the same to their father. Jason, stained by the crime, was not made king; Acastus banished him and Medea to Corinth and reclaimed Iolcus. At funeral games for Pelias, Atalanta defeated Peleus in wrestling — a favorite subject in Greek art.