Fetch the Hylotl Artifact is a quest given by Esther after turning in Find Clues to Locate the Hylotl Artifact, having scanned enough clues to unlock the location of the artifact.
Players can travel to the Grand Pagoda Library from the missions tab in their ship computer. They can use this interface to return to the mission at any time in the future to replay it.
The artifact is at the end of a sunken underwater dungeon, the Grand Pagoda Library. There are a number of hostile cultists throughout, and players must also defeat a boss at the end of the mission; Asra Nox. They'll also encounter a friendly Hylotl scholar who will help guide them through the mission named Koichi.
After defeating Asra Nox the path to the artifact is unlocked and players can recover it and return to Esther. Koichi will also join her at the Ark, offering players a set of museum side quests.
This quest is a prerequisite for Find Clues to Locate the Avian Artifact, which unlocks the Avian mission.