In Greek mythology, Laomedon was a Trojan king, son of Ilus and father of Priam and Hesione among others. He cheated Poseidon and Apollo of their wage for walling Troy, bringing plague and a sea monster on the city, then broke his promise of divine horses to Heracles for saving Hesione — prompting Heracles' first sack of Troy and Laomedon's death.
Adapted from Wikipedia, "Laomedon" · CC BY-SA 4.0
I.Family
Laomedon is son of Ilus (founder of Ilium) and thus nephew of Ganymede and Assaracus; his mother is variously Eurydice, Leucippe, or Batia. Wives named in the sources include Placia, Strymo (or Rhoeo), Zeuxippe, and Leucippe. His children include Tithonus, Priam (Podarces), Lampus, Hicetaon, Clytius, Hesione, and others; Homer also gives him a son Bucolion by the nymph Calybe.
The immortal horses in his stables descend from Zeus's gift to Tros in compensation for Ganymede.
II.Walls, monster, and Hesione
As punishment for a plot against Zeus — or as a test of Laomedon's honesty — Poseidon and Apollo served him in mortal guise and built Troy's walls for a promised wage. When he refused payment, Apollo sent plague and Poseidon a sea monster that ravaged the plain. Oracles demanded that Hesione be exposed to the monster; she was chained to the rocks.
Heracles, landing after his Amazon campaign, agreed to kill the beast for the immortal horses. He saved Hesione, but Laomedon again reneged.
III.Heracles' sack of Troy
Heracles returned with ships and allies, left Oicles to guard the fleet, and stormed the city; Telamon breached the wall first. Laomedon and his sons were killed except Podarces. Hesione, allotted to Telamon, ransomed her brother with her veil; from that "buying" (priamai) he was thereafter called Priam.
Homer already knows the cheated wages and the earlier sack; Apollodorus supplies the fullest continuous narrative. Laomedon's reign thus stands as the moral preface to Priam's Troy.