Proventus Avenicci

"He (Ulfric Stormcloak) simply walked up to the boy and murdered him."

- Proventus Avenicci, on Torygg's death.

 is Jarl Balgruuf the Greater's Steward. His daughter, Adrianne, owns Warmaiden's, a weapons and armor shop located in the Plains District of Whiterun.

Location and residence
He can usually be found standing next to the Jarl's throne, in the Jarl's War Room behind the throne, in his bedroom in the back rooms of Dragonsreach, or dining on the Great Porch. Rewards for completing bounties can be collected from him in any of these places.

Main quest
After the Dragonborn returns from killing the first dragon at the Western Watchtower with Irileth, Proventus denies the probability that they are the Dragonborn and tells the Jarl that there is no evidence to support it.

Using Unrelenting Force on him, however, does not prove this to him, and only succeeds in making everyone in Dragonsreach hostile to the Dragonborn.

General
Aside from asking for information about Whiterun, the Dragonborn can fulfill bounties for Proventus by killing giants and Bandit leaders in Whiterun Hold.

Property
Breezehome, a house in Whiterun, may be purchased from Proventus for 5000. All the furnishings needed to decorate the home are also sold by him.

Civil War
If the Dragonborn sided with the Stormcloaks during the Civil War, and takes control of Whiterun Hold during the quest Battle for Whiterun, Proventus, Hrongar, Balgruuf, and Irileth will enter exile in the Blue Palace in Solitude, and is replaced as Steward by Brill. However, if the Dragonborn kills Brill, Proventus returns to the city as steward and serves the new Jarl, Vignar Gray-Mane.

Balgruuf's Sword
Proventus' daughter, Adrianne, asks the Dragonborn to deliver a sword to him for Jarl Balgruuf. After bringing him the sword, he tells the Dragonborn he will give it to Balgruuf when "the time is right." He then equips the blade regardless. He can be heard later in conversation with Balgruuf offering the sword. Balgruuf chastises Proventus, saying "You are here to give me counsel. This is not counsel."

Quests

 * Kill the Bandit Leader

War Provisions
Proventus: "My lord, our provisions are running dangerously low. Our stores of meat, wine, and grain are all but depleted." Balgruuf: "Purchase more supplies, then. That's your job as Steward, isn't it? Why do you trouble me with these details?" Proventus: "My lord, since Ulfric Stormcloak's uprising, the cost of goods has doubled. I'll need more coin if I'm to provision us properly." Balgruuf: "Our coffers are nearly empty. I can scarcely afford to pay the guards, and we need every one of them in these troubled times. You'll have to make do with what we have, Proventus." Proventus: "Yes, my lord."

Jarl's Security
Irileth: "I am concerned about the Jarl's safety. Too many of our guards have been redeployed to fight the Stormcloaks." Proventus: "What would you have me do? If we do not send men to fight in the war, you'll find yourself guarding one of Ulfric's men." Irileth: "And if an assassin slips past the night watch, we won't have a Jarl at all. Without Balgruuf's leadership, Whiterun will descend into chaos." Proventus: "Nonsense. If Balgruuf falls, someone will take his place, for better or worse. In the meantime, we have a war to win. And win we must."

Convincing the Jarl
Hrongar: "Proventus, you must help me. We need to convince my brother to do more for the war effort." Proventus: "What would you have me do, Hrongar? Your brother is the Jarl. You know I can't question his judgement." Hrongar: "I'm not asking you to defy the Jarl, just to open his eyes. Use subtlety and suggestion to turn his thoughts to the war. You're his steward, he'll listen to you." Proventus: "Leave me out of your intrigues, Hrongar. If you have something to say to the Jarl, say it with your own tongue."

Money Issues
Proventus: "My lord Jarl, if we do not take steps soon, our coffers will be empty." Hrongar: "Raise the taxes, then! Put anyone that refuses to pay in the stocks and make an example of them." Proventus: "As you command, my lord. But, the issue could be solved another way. If we spend less on new arms and armor for the guards, for example..." Hrongar: "We're at war, old fool, or have you forgotten? Whiterun is the crown jewel of Skyrim, and you would leave us defenseless?" Proventus: "Forgive me, my lord. It was foolish of me to make such a suggestion." Note: the preceding conversation was intended to occur once Hrongar became the Jarl of Whiterun once Balgruuf was killed by children during The Whispering Door, but this stage of the quest was removed.

Quotes

 * "I serve Jarl Baalgruuf as steward."
 * "The Jarl is, as you can imagine, very busy. Perhaps I can assist you?"
 * "The task of Steward is more important than you realize. The Jarl often asks for my invaluable council."
 * "I'm kept so busy, I don't get to see my daughter as often as I'd like. Perhaps you've met her? Adrianne? She owns the shop Warmaiden's."
 * "If there's any more I can help you with, just let me know."
 * "Enjoy your visit to Dragonsreach."
 * "I'll be glad when that beast is gone from Dragonsreach. I never understood what the point of all this was." ―When Odahviing is present in Dragonsreach.
 * "Be warned, the Jarl is in a foul mood since the Stormcloaks overran Whiterun." ―After completion of Battle for Whiterun on the side of the Stormcloaks.

Bugs

 * Buying a house from Proventus may cause him to disappear upon returning to Dragonsreach.
 * Type  into the console, followed by  . Proventus should reappear.
 * Fast traveling with Proventus in proximity causes him to be teleported to the location as well.
 * The option to purchase the alchemy lab may still be present after he is paid the gold, and when you go to Breezehome, the alchemy lab will not be in place. It doesn't matter how many times a purchase is attempted, Proventus will continue to offer the upgrade but it will never appear. Also happens to Brill.
 * When the Battle for Whiterun is complete, Brill may be inexplicably dead and Proventus may remain in the Solitude Blue Palace, unable to sell you upgrades/furnishing for your house.
 * Buying a house and using the free house exploit may cause buying the upgrades to become impossible.
 * Proventus may occasionally be found in random areas in the wilderness, often found when collecting bounty from him. He will ask the player if he/she is a thief there to rob him.