The Princess Andromeda was a cruise ship captained by Luke Castellan and the primary living space for Kronos' Army. It was destroyed by Percy Jackson and Charles Beckendorf with explosives, resulting to the death of the latter. It contained Kronos' sarcophagus, and could travel faster then any mortal ship, possibly assisted by magic or a Titan. The Princess Andromeda contained all sorts of monsters, including Dracaenae and Drakons.
Luke is in control of the ship. Hermes sends Percy onto it so he can talk to Luke, which Hermes leaves Percy to do himself. The ship has many human mortals on it, but they are all under some sort of trance (possibly the Mist) that prevents them from seeing the monsters inhabiting the ship. After Percy, Annabeth Chase, Grover Underwood, Tyson, and Clarisse La Rue take the Golden Fleece from Polyphemus' island in the Sea of Monsters and return to Miami, Luke confronts Percy to take the fleece from him. However, Percy tells him that he doesn't have the Golden Fleece anymore nor does Annabeth, Grover, or his Cyclops half-brother, Tyson. He informs him that they had let Clarisse fly home with it ahead of them. The Party Ponies attack at the right moment once Luke made a mistake and said, "Kronos was right. You should have been killed, Percy." Putting Kronos' army in confusion when Luke and Percy are dueling to the death. Along with the Party Ponies was Chiron who saved Percy, Annabeth, Grover, and Tyson from another fight with Luke and his army aboard the Princess Andromeda.
Percy and Beckendorf board the ship, with the intention of destroying it with Greek fire. They notice that it is filled with Telekhines and other members of the Titan Army, and that the once plush carpets had been ruined by slime. There are no more mortals on the ship which Percy thinks didn't get to leave with their bingo winnings. Their time is cut short when two Telekhines enter the engine room while they are planting the explosives. Percy buys Beckendorf some more time by running through the heavily armed crowds of monsters and is caught by Luke/Kronos. Then Beckendorf is forced on the deck as two monsters claim they captured him heading for the engine room to plant explosives. Percy (and Luke shortly after) figure out that Beckendorf pretended to head back to the engine room so they wouldn't send anyone to check. Beckendorf activates the trigger to the explosives and Percy escapes by jumping into the sea, but Beckendorf is not so lucky. While the plan to destroy the Princess Andromeda was a success, Percy thinks that it was too easy, which is true as Luke was only using it to give the demigods a false sense of security.
The boat is named after the Aethiopian princess Andromeda, daughter of King Cepheus and Queen Cassiopeia. When her mother, Queen Cassiopeia boasted that Andromeda was more beautiful than the Nereids, she angered the god Poseidon, who sent a sea monster to ravage her kingdom as punishment. Desperate, King Cepheus went to consult the Oracle of Delphi, who stated that Andromeda must be offered as a sacrifice to the sea monster in order to appease Poseidon; Andromeda was then chained to a rock by the shore. However, Perseus, the son of Zeus, found her and freed her. Then, during the wedding, Andromeda's former suitor Phineus arrived with an army of 200 men. In retaliation, Perseus killed the attackers with Medusa's Head, taking it from its cloth and showing it to all those that looked at it, turning the army to stone instantly. Upon his return to Greece, Perseus married Andromeda, with whom he had seven sons and two daughters; one of their sons, named Perses, stayed behind in Aethiopia to rule his grandfather's kingdom when he died, later becoming the ancestor of the Persians.