In the Penacony version of Honkai: Star Rail, Sunday once cast a hex on Aventurine, meaning that if he ever lied, the Harmony would not reject him.
In other words, when the time truly came, Aventurine would lose his sense of self and become a member of the Harmony.
And what The Choir was doing right now was "harmonizing" the consciousness of the entire school of Demonic Orcas before them. They would forever lose their sense of self, becoming members of the Harmony family.
Chapter 165