Gard

Miss Gard, whose real name is Sigrun, is a Valkyrie and security consultant of the Supernatural. She first appears in Death Masks.

Description
Gard is a Valkyrie who works for Monoc Securities and Donar Vadderung. She works for Johnny Marcone as a magical security consultant. (ref) Throughout a series, there's a hinted romantic relationship with Hendricks.(refs?)

She is described as being unusually tall—"Amazonian"— blonde, athletic, and "coldly beautiful". She tends to be eerily calm in stressful situations, scarily practical, and more paranoid than Marcone. According to Mab, she is clever and resourceful.

She has, at various points in the series, used a sword and shield, a double-bladed axe, and an assault rifle. She knows how to fly a helicopter, and does so in both Death Masks and Small Favor to the tune of "Ride of the Valkyrie".

She is also a skilled wielder of magic, though her magic seems to be connected to old Norse runes, and she appears to be especially proficient at wards and defensive-type spells. (ref?) She can open a door into the Nevernever with her knife.

In Heorot, Gard reveals that she's the scion of the Geats; presumably of Beowulf himself; Mab called her the "Chooser". Her status as a Valkyrie makes her very resilient, as witnessed by the fact that she's eviscerated in Small Favor but manages to get well again very quickly. She is an immortal, in that she does not age, though presumably she can still die from fatal injuries. (ref?) As a Chooser of The Slain, she has the innate ability to know when people are going to die, though this is not set in stone as the future is always changing (however, according to her, "there will be consequences").

Death Masks
In Death Masks, Harry is introduced to her by Marcone during the Chicago Historical & Art Society gala at the Marriott Downtown Chicago Hotel. Harry deduces that Gard was responsible for the ward that tore up Bob when he investigated Marcone's Estate.

Dead Beat
In Dead Beat, Gard saves Harry from Li Xian who was ordered to kill him by Corpsetaker.

White Night
In White Night, Gard was "on an assignment elsewhere". (ref?)

"Heorot"
In "Heorot", Gard, Harry Dresden and Mouse seek and rescue Elizabeth Braddock after she was abducted by a Grendelkin. She was taken from a Brewfest and McAnally told Harry about it.

"Even Hand"
In "Even Hand", (needs notes)

Small Favor
In Small Favor, Harry followed a lead given him by Ms. Demeter at the Executive Priority Health club to find a badly wounded Gard and Hendricks hiding in a secret house. While there, they are attacked by Denarians led by Polonius Lartessa ("Mantis Girl"). Harry took her and Hendricks, along with Akariel's coin to Michael Carpenter’s home for safe-keeping. Harry talked with Gard about a possible traitor in Gentleman Marcone's organization, Torelli in particular. Gard gives Harry the combination and locker number at Union Station for her collection of blood samples of Marcone and Torelli. After the battle at the Shedd Aquarium, Gard took a badly wounded Kincaid to a safe house. Gard flew a reconditioned Huey to Demonreach for rescue pick-up of Marcone, Ivy and Harry's team. She played "Ride of the Valkyries" over the loud speakers. Michael Carpenter is badly wounded by gunfire being cabled up to the helicopter.

Changes
In Changes, Gard takes Harry to Monoc Securities to meet with Donar Vadderung for the first time. While there he sees Soldiers of Valhalla and meets Hugin and Munin.

"Aftermath"
In "Aftermath", Gard gives some assistance to Karrin Murphy in trying to rescue Georgia and Andi from the Fomor. Gard told Murphy that if she wanted, Marcone could get her police badge back but Murphy refuses. Gard then tells her that Monoc Securities is hiring and Vadderung would likely be interested in her.

Ghost Story
In Ghost Story, Gard, Hendricks, Marcone and all of his troubleshooters have alibis at the time of Harry's shooting.

Mythological significance
"Sigrun" is arguably one of the best-known Valkyries in Norse Mythology, and a major character in the saga of Helgi Hundingsbane, found in the Poetic Edda. It's unknown whether she's the same figure or not.