Icarus

Icarus was the son of Daedalus, cousin of Perdix, and the grandson of Athena. He is most commonly known for his attempt to escape Crete by flight, which ended in a fall to his death because he did not listen to his father.

History
He and his father were held captive by King Minos, after Minos' daoughter,Ariadne, helped Theseus, son of Poseidon, defeat the Minotaur, Icarus escaped on one of his fathers inventions: wings made of metal feathers and wax. Ignoring Daedalus' advice, Icarus flew too high and the sun melted the wax holding the feathers together and the wings fell apart, causing Icarus to plummet to his death over the ocean.

Post-Modern
In the Percy Jackson series, after Icarus' death, Daedalus was full of despair and became jealous of his nephew's intelligence and skill. After Perdix showed Daedalus some plans for an automaton that could host a human soul, he killed Perdix causing him to fall out a window (by making him stretch too far). He was then punished by Icarus' grandmother, Athena who watched the event unfold. Athena marks him as a murderer. This mark appears even when he changes bodies that were made from Icarus' designs.

Percy dreamt of both Icarus' fall and Perdix's death in dreams before finally meeting Daedalus himself.