The Seven Demigods are a group of demigods from the 'Heroes of Olympus' book series by Rick Riordan. The Seven consist of:
Percy
Jackson, the son of Poseidon.
Annabeth
Chase, the daughter of Athena.
Leo Valdez, the son of Hephaestus.
Jason Grace, the son of Jupiter.
Piper McLean, the daughter of Aphrodite.
Hazel Levesque, the daughter of
Pluto.
And:
Frank Zhang, son of
Mars.
They are all following 'The Prophecy of Seven' which is:
Seven Half-Bloods shall answer the call,
To
storm or fire the world must fall.
And oath to keep with a final breath,
And foes bear arms to the doors of death.
They all ride from place to place on the Argo II. Which is captained by
Leo, who also designed and built it. The Argo II is a massive flying boat that has a mechanical dragon head called Festus as the figure head.
The Sevens quest is to prevent Gaia from rising and destroying the world.
The Seven Demigods paraded through the camp, other demigods cheering as they
passed. They had done it, they had defeated
Gaia.