The first time the player 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 jokes, saying he'd sooner bend his knee to Ulfric Stormcloak. Adrianne finally gives in, and agrees to make the weapons.
Idolaf will ask if the player is a Battle-Born or Gray-Mane. If they reply by saying they are a Battle-Born, he will treat them as a friend, but if they reply saying they're a 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". If the player kills Idolaf, then the Battle-Born clan will send hired thugs after him. Also after killing him, the player will receive a letter of thanks from Avulstein Gray-Mane if they have completed the quest Missing in Action.
- Idolaf can be persuaded in the quest Missing in Action. He'll explain that he and Thorald Grey-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 player as proof, saying that Thorald's family is better off believing he's dead.
- Idolaf may die, and grant the Dragonborn with an inheritance of 100 gold. This will be delivered by courier along with a "letter of inheritance" (happened after saying Battle-Born to him, and completing several companions quests without speaking to Jarl Balgruuf yet. Unsure of whether this is coincidence or related.)
- If the Dragonborn replies with "Battle-Born" when Idolaf asks them which they are, and joins the Legion, Idolaf may attend your wedding in Riften. When prompting to speak with him after your marriage in Whiterun, he may give you a gift of ale. Oddly enough, Olfirid Battle-born or anybody else won't.
- The Elder Scrolls V: Skyrim (First appearance)