Fifth Eye has informed you that the Voices of Nerat would like to speak with you back at Cacophony. He has a plan to destroy Graven Ashe that he would very much like to discuss with you.
Head to Cacophony to talk to Voices of Nerat. It will ask you to seek Ashe out and kill him, promising the highest honor. With Subterfuge 59, you can ask if it means absorption by Nerat. He will confirm it (what).
Go to Iron Hearth and slay Graven Ashe and his followers. Listen to his last words, then return to Nerat.
Of course, Nerat is jubilant at Ashe's death - and thoroughly unhinged, more than usual. Your choice is to fight it directly... Or you can choose another route. By offering to swear fealty to Nerat, you can peacefully overcome the Archon - after sacrificing a companion. Nerat's unhinged nature allows you to seize control over the Archon if you let it consume one whose loyalty is 4 or higher:
Voices of Barik reforms the Scarlet Chorus into a powerful army, combining his Northern heritage with the size and ruthlessness of the Chorus.
Voices of Verse makes the Chorus ever bigger and more powerful.
Voices of Lantry turns the Chorus into a gigantic university and Sage guild, busy transferring the knowledge Nerat accumulated over the centuries.
Voices of Eb has two possible endings, after she liberates the Tiersmen pressed into service. If you destroyed the Tidecasters during the Conquest, she dismantles the Chorus and disappears into the Northern Empire, becoming a boogeyman. If you let them be consumed by Nerat, the Chorus is transformed into a new guild of the Tidecasters, as Eb combined with the memories of her former mentors restores it to its former glory and then surpasses it.
Voices of Kills-in-Shadow turns the Chorus into the Scarlet Hunters, making them one of the biggest and deadliest armies on Terratus, prosecuting war against the Northern Empire.
Voices of Sirin turns the Chorus into a demented freak show, eventually caving in on itself.