Each of your nine companions has a unique personal questline that delves into their backstory, motivations, and relationships. Completing these quests often unlocks new abilities, strengthens their loyalty, and can even lead to romantic relationships. Talk to your companions frequently at Skyhold to trigger these quests. Examples include 'Unfinished Business' for Varric, 'Guarding the Coast' for Blackwall, and 'The Iron Bull's Chargers' for Iron Bull. These quests are often deeply personal and offer significant lore insights.
