After meeting Han, if asked why he doesn't wear a collar, he will reveal to know someone that is able to remove them.Speak again to Nebora that will be now willing to help you and that will offer to remove the collar of the main character.
Become the champion of the underground arena at the Fort Joy kitchen (see The Arena of Fort Joy).Speak to Nebora that will reveal to be able to remove the collar but also that don't consider you worth of the service.Convince Leya to remove the Source Collar of all characters.Convince Nebora to remove the Source Collar of the main character.Remove the Source Collars, allowing that characters to equip amulets.Find someone that may help in removing the Source Collar.This is one of the main quests automatically acquired at the beginning of the game. The Collar is a main Quest in Divinity: Original Sin II.