This quest is unlocked by completing the quest “A New Playing Field” (https://youtu.be/qKJpsZTQQDo) as well as achieving Rank 16.
Shadowbringers Relic Quest Playlist: https://www.youtube.com/playlist?list=PLAIwJ_87EVatVH51HDvwwZOQdUcJxcTNV
source
This quest is unlocked by completing the quest “A New Playing Field” (https://youtu.be/qKJpsZTQQDo) as well as achieving Rank 16.
Shadowbringers Relic Quest Playlist: https://www.youtube.com/playlist?list=PLAIwJ_87EVatVH51HDvwwZOQdUcJxcTNV
source