For those who have not completed games in the Xenoblade Chronicles series, this page contains spoilers regarding the plot. Discretion is advised.
The Ancient Ship (Japanese: 古代船, Kodai-sen) is a story-exclusive area in Xenoblade Chronicles 2. It is located in an uncharted region of Alrest. It is impossible to return to the Ancient Ship after Chapter 1.
The Ancient Ship was once a Tornan ship belonging to Addam. After the Aegis War ended, Addam sealed the Aegis Pyra in it and sank it, intending that she would be reawakened only when mankind truly deserved her power.
Five hundred years later, the organization Torna, lead by Jin, recruits the help of several Salvagers from the Argentum Trade Guild, including Rex, to grant them access to the ship, as they want to recover the Aegis. After the ship resurfaces, Jin, Malos and Nia go inside with Rex, since they require a Leftherian to grant them access to the chamber in which the Aegis lies in stasis.
Torna's plan fails as Rex awakens Pyra despite having been killed by Jin, and Pyra escapes Torna's clutches with Rex and Nia.