Upon landing on an island near Bear Mountain, Jason and the Argonauts encounter the Gegeines, who raided their ship when the others went into the forest to find supplies. Hercules was among the Argonauts guarding the ship at the time and managed to slay some of them until Jason returned. Once some of the other Gegeines were killed, the Argonauts set sail.
The Gegeines are the servants of the Giants and were born from the Earth as shock-troops for the Giants during the original Giant War. Once Jason Grace, Piper McLean, and Leo Valdez got to Mount Diablo, they met the giant Enceladus, who summoned Earthborn straight from the ground. Leo destroyed five of them with construction equipment, and the last one was destroyed by Piper. Apparently, after they were vanquished, they "left some pieces of loincloth behind".After Jason, Leo, and Piper's helicopter got destroyed, Thalia Grace met up with them at the Wolf House. She told them about how they were surrounded now, and then killed one of the Earthborn that was sneaking up on her with her final arrow. Later, Piper and Leo fought the rest of them, successfully returning all of them to the pits of Tartarus. However, after Porphyrion rose, they came back to life.
During the battle at Camp Jupiter, they were fired on by scorpion ballistae and water cannons, but they continued to push the Romans back before Percy and Frank rallied the Fifth and Third Cohorts to attack them. A large number of Earthborn were destroyed when Percy used the eagle standard to kill a huge number of monsters. The remainder were presumed to have been killed or fled after the battle. While Percy is running from Polybotes, Tyson is seen battling an Earthborn with Ella's help.
Gegeines look like clay statues of giants that have six arms. They are seven to eight feet tall. They have superhuman strength, and can generate large and surprisingly sharp rocks in their hands.
- According to Ella, the groin of an Earthborn is sensitive. It is unknown if this is true or not, but it is likely so, since she is very knowledgeable.
- Unlike most monsters, when the Gegeines are defeated, they melt into clay instead of turning to dust.
|Species:||Centaur | Cyclopes | Dragon | Drakon | Empousa | Giants | Harpy | Hyperborean Giant | Ichthyocentaur | Karpoi | Laistrygonian Giant | Pegasus | Skolopendra | Stymphalian Birds | Telekhine | Satyr | Merpeople | Gorgon | Fire-Breathing Horse | Katobleps | Nymphs|
|Friendly Monsters:||Argus | Blackjack | Briares | Chiron | Don | Ella | Festus | Gleeson Hedge | Grover Underwood | Hippocampus | Mellie | Mrs. O'Leary | Ophiotaurus | Peleus | Scipio | Tyson | Tempest|
|Enemy Monsters:||Agrius and Oreius | Arachne | Basilisk | Charybdis and Scylla | Chimera | Chrysaor | Clazmonian Sow | Colchis Bull | Echidna | Euryale | Geryon | Joe Bob | Kampê | Manticore | Medusa | Minotaur | Nemean Lion | Polyphemus | Sphinx | Stheno | Typhon ||
|Neutral Monsters:||Cerberus | Erymanthian Boar | Gray Sisters | Gorgons | Furies | Flesh-Eating Horse | Gryphon | Hippocampus | Siren | Carnivorous Sheep|