|“||Seek the caverns, near the springs of blue. Oh, Apollo.....your sanity will be taken away, but do not.....||”|
Hyacinthus, also known as Hyacinth, was a divine hero who was loved by both Apollo and Zephyros. While playing a game of quoits with Apollo, Hyacinthus was accidentally killed by a jealous Zephyros. In his grief, Apollo refused to allow Hades to take Hyacinthus. He transformed the mortal into a flower, which became known as a hyacinth, named after him. As a penitence, Zephyros is forced into the service of the god of love, Eros.
While trying to retrieve Diocletian's sceptre, Jason Grace and Nico di Angelo meet with Zephyros, still in the service of Eros. Zephyros, in his Roman aspect Favonius, provides an explanation as to why he serves the god of love. He recounts the story of Hyacinthus. He tells about the jealousy he had felt for Apollo and Hyacinth's closeness. Jason is initially surprised by Favonius's falling in love with a man, but he recovers quickly.
Hyacinthus is mentioned many times by Apollo throughout the book.
When Nosoi (plague spirits) attack Apollo on his way to Camp Half-Blood, he gets flashbacks of the events that occurred on the day Hyacinthus died.
Apollo also confesses that Hyacinthus and Daphne are his greatest and favourite lovers. Apollo tells that he is reminded of the few months he spent with Hyacinthus when he sees his son Will Solace with his boyfriend Nico di Angelo.
After his meeting with Rhea, Apollo falls into a dream where Hyacinthus appears as a ghost, talks to him for a very brief time and asks him to find the caverns near the blue springs. When Hyacinthus starts fading away from the dream, Apollo desperately reaches and grabs his lover's shoulder and begs him not to leave him. But he wakes up, holding a pot of hyacinth flowers and later, comes to know he was talking to the flowers.
When Apollo sings to tackle the Myrmekes, he sings of his love for Hyacinthus and expresses his regret over his jealousy which ultimately killed Hyacinthus. He also tells that he created the hyacinth flowers out of his dead lover's blood, to always keep him in the sunlight.
Apollo continuously grieves for the loss of Hyacinthus, as he is constantly reminded of him everywhere he goes while in human form.
When Apollo meets Meg McCaffrey again, he says that he had never been so happy to see anyone, including Hyacinthus in his amazing tuxedo on their date night.
Hyacinthus is described to be quite handsome. Apollo names him as the most handsome among the men he has met.
Hyacinthus was seen to have copper or bronze skin, curly black hair and eyes as purple as senatorial robes. He had kind and brilliant smile in Apollo's flashbacks.
In Apollo's dream, however, he is seen to have an ugly dent above his left ear, where the discus had struck him.
- The hyacinth flowers Apollo held were either red as the blood of Hyacinthus or had the violet hue of his eyes.
- When Hyacinth tells Apollo to find the caverns near the blue springs, he was referring to the Cave of Trophonius.