The Trial of Brother Devin

The Trial of Brother Devin is a side quest in the Fallout 4 add-on Far Harbor.

Detailed walkthrough
Zealot Ware explains that Brother Devin is fasting and is only using irradiated water for several days now, waiting for a sign of Atom. He also explains that he and Devin are the only two not born with radiation sickness and thus radiation hurts them. He asks the Sole Survivor to convince Brother Devin to stop with fasting in order to help him survive. With a very hard persuasion check he can be convinced that the Sole Survivor is Atom's messenger and can be persuaded to stop fasting. If the attempt fails, dressing in Child of Atom rags, wearing a Sack hood, and heavily irradiating yourself (75% of your total health) is enough to convince him.