Harry Dresden describes Uriel as aggravating and scary; with something "hideously absolute" about him, unyielding and unchanging, that makes Dresden feel fragile. Dresden also calls him the Spymaster, and describes him as Heaven's spook.
Mab calls him the Watchman, and describes him as the one who works in the shadows, acting inconspicuously. Uriel is the quietest and likely the most dangerous archangel. Bob and Dresden considers him as Heaven's Black-Ops, and Bob is of the opinion that Dresden's receiving a favor from him is not a good thing.
One of Uriel's main tasks is to preserve free will, often employing dead spirits in a metaphorical police stations. He is peers with Mab. He also occasionally visits Dresden with annoying, cryptic advice.
In Changes, Uriel appears as a tall, young man wearing a tee shirt and jeans and a farmer's duck coat. His blond hair falls over his guileless blue eyes. He snorts when laughing in a non-angelic way.
In Ghost Story, Uriel appears as a young man with dark gold hair that hung messily over silver blue eyes and sharp cheekbones. He wears jeans, old boots, a white shirt, and denim jacket, standing with utter stillness.
Harry Dresden claims that Uriel has the power to destroy the solar system. Uriel quickly corrects him, stating bluntly that he could annihilate galaxies. The extreme restrictions on Uriel's usage of his immense powers, however, severely limit his effective influence in the mortal world, generally to a level below that of his Sidhe contemporaries such as Mab. Due to such limits, Uriel is forced (at first) to walk away angry from a confrontation with the significantly less powerful, but (technically) mortal Nicodemus Archleone, who challenges him directly.
Uriel is able to entrust his power to a mortal, though with ruinous consequences should the power be abused; in this case, Uriel would Fall.
In the series
In Small Favor, Uriel grants Harry Dresden the power of Soulfire sometime early in or before the events of Small Favor. He appears in the hospital's chapel as a little old janitor, named Jake. He talks about God and gives advice before disappearing suddenly and leaving behind the janitor's cart with a copy of The Two Towers.
In "The Warrior", Uriel appears again as Jake the janitor. He informs Harry Dresden that the events which had transpired did not have so much to do with Father Douglas, but rather that Dresden's smaller actions have influenced many other people, among which Courtney and both her parents, second baseperson Kelly and those she is going to help as a counselor. Dresden also stopped Michael Carpenter from going too far with Father Douglas.
Dresden tries to bill Uriel for his time, without success.
Love your child, Dresden. Everything else flows from there. A wise man said that. Whatever you do, do it for love. If you keep to that you will never wander so far from the light that you can never return.— Uriel
In Changes, Dresden summons Uriel after being severely wounded. Uriel regretfully informs Dresden that he can't fix his back, that he is limited to what he has already done. He does tell Dresden that Maggie is still alive, confirming that she is indeed Dresden's daughter.
In Ghost Story, Bob informs Dresden that Uriel is the "black-ops guy" of the archangels and has conned the Father of Lies. He suggests that Uriel may also be scamming Dresden and colluding with Mab in some way.
After Dresden remembers who ordered the hit on him, Uriel freezes time in order to have a chat. He leads Dresden to the fact that a Fallen Angel whispered a lie into his ear which compromised his freedom of choice. Uriel chastises an unfazed Collin Murphy for misrepresenting the truth to Dresden before stating that humankind always manage to find a way to try his patience. When Dresden calls him "Uri" (leaving off the "el" part), Uriel is insulted, saying that the part is important to who and what he is. He is however, comfortable with being called "Mr. Sunshine", forgives Dresden and offers him a job. To help Dresden make an informed choice about the job offer, Uriel showed him his friends and family to make sure they are alright.
In Skin Game, Uriel freezes time briefly when Michael Carpenter surrenders himself to Nicodemus Archleone in exchange for letting his friends go. He appears as a tall, lean, and broad-shouldered man, with dark black hair, dark skin and silver-green eyes. Uriel tells Carpenter that he does not have to give up his protection, that he has already given enough and that Archleone will torture him. Carpenter calls Uriel his friend and continues. Archleone taps Uriel on the shoulder and tells him to stand aside, unimpressed by Uriel’s threats as he knows that the angel cannot act against him. He goes so far as to flick Uriel’s nose, daring the angel to smite him. Uriel backs down and speaks to Waldo Butters, before silently asking Harry Dresden to buy him some time. Dresden antagonizes Archleone, allowing Uriel to approach Carpenter and heal him. Butters meanwhile, retrieves Amoracchius and gives it to Carpenter. Archleone claims that Uriel has cheated but retreats when faced with the restored Carpenter.
Dresden demands that Uriel heal the injured Karrin Murphy, but he states that he is unable to. Helping out by collecting towels and tools for Butters to treat Murphy, Uriel also tells Dresden that he cannot provide a protection detail for her in the hospital. Dresden faints and in the process accidentally hits Uriel in the nose, which starts to bleed. Uriel tells the group that he has loaned Carpenter his Grace. Dresden, shocked, remarks that Uriel has the power to unmake Solar Systems which Uriel corrects to Galaxies. As his options were limited, he could not directly interfere, but he could help Carpenter to do so. Dresden equates the action with loaning someone a giant passenger jet because they needed a reading light. As a consequence of this, Uriel is now mortal and can be killed while if Carpenter were to misuse the Grace, Uriel would Fall.
Carpenter offers to return the Grace, but Dresden helps him see that Uriel would not do such a thing on a whim – that more important things are in the works. He says it has something to do with Archleone’s attempt to steal the Holy Grail and that he knows he is on the right track because Uriel doesn’t answer with words. During the heist, Carpenter makes a loud, resonating warning to the group before they enter the underworld, telling them to "choose carefully". Though Carpenter claims that the message was probably not for himself and Dresden, the wizard spots Uriel’s manipulations at work and thinks that maybe it was.
After escaping Hades' Vault, Archleone goes after Carpenter’s family. Uriel, still without his grace, prepares to assist in the defense of the Carpenter home with a kitchen knife. Charity Carpenter tells him that he should be upstairs with the children, to which he replies "I was fighting wars when this planet was nothing but expanding gases." Dresden points out that he was not vulnerable back then and assigns Mouse to stay with him. When some of Archleone’s squires take Charity, Uriel kills one using the kitchen knife. Though his actions are that of a professional, he looks sickened as he does so. Butters manages to wield the remains of Fidelacchius, which Uriel observes with great satisfaction.
Uriel’s grace returns the following day and he speaks with Dresden privately. He is relieved that Goodman Grey did not try and step foot inside the Carpenter’s front yard as it would have been “awkward”. He confirms to Dresden that his angle throughout the events was the redemption of Archleone, Jordan and the other squires, as well as seeing Butters become a Knight of the Cross. He was not expecting Fidelacchius to resemble a lightsaber, but admits that he did enjoy the music of Star Wars. Uriel claims that his job is making it possible for mortals to make choices.