The Lost Hero, The Son Of Neptune, The Mark of Athena

All about "Heroes of the Olympus"
Percy Jackson
son of Poseidon. he has a celestial bronze sword named Riptide. he has been missing for three days and is apparently "The Lost Hero". Percy was sent to the Roman Camp by Hera, just as Jason had been sent to the Greek camp (the exchange of leaders).
Annabeth Chase
a 16 year old daughter of Athena (a main character from the previous series). she arrives in a flying chariot with a demigod with a demigod named Butch, on account of the dream Hera sent her, telling her to go there and find someone with one shoe in order to find her boyfriend, Percy Jackson, who has been missing for three days.
Jason Grace
15 year old son of Jupiter who lost his memory. the younger brother of thalia grace., is the son of Jupiter/Zeus, brother of Thalia Grace, from roman version of camp half blood, slew the titan Krios. weapon: a coin that could change into a double-edged sword or a javelin-like lance
Piper Mclean
daughter of Aphrodite and girlfriend of Jason, can charm speak, father is Tristan McLean weapon: Katoptris, is a ceremonial knife, used by Helen of Troy
Leo Valdez
jason's demigod best friend. son of hephaestus. likes to build things and is constantly busy with tools. the firat fire user in hundreds of years. he is fireproof, fire cannot hurt him. he becomes leader of the hephaestus after the quest.
Hazel Levesque
Daughter of Pluto/Hades. Born in 1940 and died in 1952 but was reincarnated when Thanatos was kidnapped by Alcyoneus and the Doors of Death were opened.
Frank Zhang
Son of Mars/Ares. He can turn into anything because of one of his ancestors.
The centaur who trained Hercules. He was the teacher of many Greek heroes and when he died, Zeus placed him among the stars as the constellation Sagittarius. He also wasn't mean and nasty like most centaurs.
(Greek mythology) the supreme god of ancient Greek mythology
(Greek mythology) the god of the sea and earthquakes in ancient mythology
(Greek mythology) the god of the underworld in ancient mythology
(Greek mythology) Greek god of war
goddess of love and beauty and daughter of Zeus in ancient mythology
(Greek mythology) goddess of wisdom and useful arts and prudent warfare