The Collar Edit
This quest is automatically obtained when you start the game.
One way to remove the collar and get rid of the Source-Muted status is to win in the Arena below the kitchen in Fort Joy. After earning the title of 'The One', explain to the NPC Nebora near the waypoint shrine in Fort Joy (x223 y182) that you have won in the arena. She will remove the collar on your main character only.
You can also remove everyone in your party's collars at the Seeker Camp. Speak to the NPC's Leya & Duggan (x441 y17) after you've saved their leader Gareth.