Reformation

During the quest “The Way Life Should Be”, you should confront DiMA about replacing Avery with a synth. If you agree to keep it a secret, DiMA will then tell you about a plan to replace High Confessor Tektus with a synth to ensure the peace between all factions in the island. Agreeing to this plan will initiate the quest. You'll also receive Acadia's Shield from DiMA by completing the previous quest peacefully.

First, you have to find the previous High Confessor Martin’s holotapes from his hideout and bring them back to DiMA for manipulation. Head to the marked location SW of the Echo Lake Lumber Mill then find a drainage pipe that you can enter. Enter the door leading to pump control using the Worn Key DiMA gave you. Grab the two holotapes then leave the place. Return to Acadia then bring the holotapes to DiMA for editing.

Now you have to travel to The Nucleus and talk to High Confessor Tektus. He'll ask you to play the edited holotape DiMA gave you. You can then meet up with him in the command center where you can kill him secretly. Alternatively, you can pass a speech check to force him to leave instead.

Return to Acadia where you’ll find DiMA is talking with the synth replacement. Talk to him to receive a good amount of caps and the Protector of Acadia perk as reward for completing the mission. If you have pending tasks for the quest “Cleansing the Land”, they'll be completed alongside that quest.

Talk to Tektus in The Nucleus to receive Atom’s Bulwark as well. Finally, return to Far Harbor to find Avery telling everyone that peace has been made with the Children of Atom and you’ll receive a good amount of caps as well from her as bonus.