In Horizon Forbidden West, the Cradle of Echoes quest is the main quest after the Broken Sky and the Kulrut quest. The Cradle of Echoes will help solve a series of mysteries surrounding the High Zenith and what Aloy has observed in the other High Zenith facility. The Cradle of Echoes is another High Zenith facility.
At the end of the Cradle of Echoes quest, Aloy get the code from the Cradle of Echoes quest, and is almost ready to know who the asset is.