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.