In Greek mythology, Idmon was an Argonaut seer who foresaw his own death yet sailed with Jason. Sources make him son of Apollo (by Cyrene, Asteria, or others) or give him a mortal father Abas; among the Mariandyni a boar gored him. Distinct from other figures named Idmon (Arachne's father, a Danaid husband, Turnus's herald).
Adapted from Wikipedia, "Idmon (Argonaut)" · CC BY-SA 4.0
I.Seer on the Argo
Idmon joined the Argonauts knowing from bird-omens that he would not return. Apollonius places him among the seers of the voyage; Apollodorus and Hyginus likewise count him in the crew. Parentage varies: Apollo and the nymph Cyrene (Hyginus), Apollo and Asteria, or a mortal Abas as father in some notices — the atlas records the Apollo–Cyrene and Abas forks as a sourced dispute on the character.
On the outbound voyage, in the land of the Mariandyni in Bithynia, a boar killed him while he was gathering straw. Idas later slew the beast. In 559 BCE the citizens of Megara Heraclea (modern Ereğli) are said to have built a temple over his grave.
II.Homonyms
The atlas id idmon is the Argonaut seer. Wikipedia also lists Idmon son of Aegyptus (killed by a Danaid), Idmon father of Arachne, a herald of Turnus in the Aeneid, and a minor Epidaurian in Statius — none of those share this node.