The first time the Dragonborn walks into Whiterun, Idolaf will be trying to make a deal with Adrianne Avennici, saying that he needs her to forge more weapons for the Imperial Legion. She complains, saying that she cannot make that many swords. After, she tries to persuade Idolaf to go and ask rival clan member Eorlund Gray-Mane to make some. He then says he'd sooner bend his knee to Ulfric Stormcloak. Adrianne finally gives in, and agrees to make the weapons.
Idolaf will ask if the Dragonborn whether they prefer the Battle-Borns or Gray-Manes. If they reply by saying 'Battle-Born,' he will treat them as a friend, but if they reply with 'Gray-Mane,' he will dislike them and say, "I should bash your face in for what you've done." If they say that they don't pick sides, he will say, "Sooner or later, we all have to choose a side."
Adrianne: "I just can't fill an order that size on my own. Why don't you swallow that stubborn pride of yours and ask Eorlund Gray-Mane for help?"
Idolaf: "Ha! I'd sooner bend my knee to Ulfric Stormcloak. Besides, Gray-Mane would never make steel for the Legion."
Adrianne: "Have it your way. I'll take the job, but don't expect a miracle."
Olfrid "Foolish old woman! You know nothing! Nothing of our struggles, our suffering!"
Fralia "Nothing? And what of my son, hmm? What of Thorald? Is he nothing? So don't talk to me about suffering!"
Idolaf "Your son chose his side, and he chose poorly. And now he's gone. Such is the way of war. The sooner you accept his loss, the better."
Fralia "I will never accept his death! My son still lives. I feel it in my heart. So tell me, Battle-Borns, where is he? Where are you holding my Thorald?"
Olfrid "[to son] Do you believe this old hag? [to Fralia] "Holding him"? Why, I've got him in my cellar. He's my prisoner. Face it, cow! Your stupid son is dead! He died a Stormcloak traitor. And you...you best keep your mouth shut before you suffer the same."
Idolaf "Come on, father. There's nothing more to be said here."
- "Damn those Gray-Manes to Oblivion. They want to back the Stormcloaks, they'll get what's coming to them."
- "Avulstein Gray-Mane and I were best friends as children. If I see that traitor again, I'll throw him in jail myself!"
- "The cold, frightening truth is that the Empire represents progress. Anyone who fears progress is a coward."
- "The Stormcloaks are content to live in the past forever. No wonder the Provincials think we're all baseless savages."
- Idolaf can be persuaded in the quest Missing in Action. He'll explain that he and Thorald Gray-Mane used to be friends as children and that he looked into his disappearance, until he received the Imperial Missive. He'll then give it to the Dragonborn as proof, saying that Thorald's family is better off believing he's dead.
- If Idolaf dies, the Dragonborn may receive a Letter of Inheritance and 100 (minus the Jarl's 10 tax) if they were on good terms with the deceased.
- If the Dragonborn kills Idolaf, the Battle-Born clan may send hired thugs after them. The Dragonborn will also receive a letter of thanks from Avulstein Gray-Mane if they have completed the quest Missing in Action.
- If the Dragonborn is on good terms with Idolaf and joins the Legion, Idolaf may attend their wedding in Riften. When prompting to speak with him in Whiterun after the marriage, he may give them a gift of ale, or a copy of Nords Arise!
- Although it is never explicitly stated, he is almost certainly a member of the Imperial Legion, judging by his attire and request for weapons from Adrianne for the Legion.
- If a member of his family has been attacked or killed by the Dragonborn, he will approach them in the streets of Whiterun with his sword drawn, giving three chances to apologize. If no apology is made, he will initiate a fight there to the death. If he attacks, passersby will support the victim.
- If the Dragonborn sided with Battle-Born when asked by him, he will consider Dragonborn as his friend. Thus almost all items in the House of Clan Battle-Born can be taken without penalty except for some leveled potions.