Arctis Tor

Arctis Tor is the capital of the Winter Court of Faeries in the Nevernever.

Description
"Mab’s stronghold was a fortress of black ice, an enormous, shadowy cube sitting high up the slope of the highest mountain in sight. A single, elegant spire rose above the rest of the structure. Flickers of green and amethyst energy played within the ice of the walls. I couldn’t make a good guess at how big the thing was. The walls and battlements were lined with inverted icicles. They made me think of the fanged jaws of a hungry predator." 

Proven Guilty
In Proven Guilty, Thorned Namshiel attacked it with Hellfire while serving on the Black Council. Evidence of acid attacks similar to those used by Shagnasty the naagloshii, another Black Council operative, was also observed by Harry Dresden.

Harry Dresden, Charity Carpenter, Karrin Murphy and Thomas Raith reach Arctis Tor to rescue Molly Carpenter who was abducted by the Scarecrow, a Fetch and a phobophage who took her there. As they approached, Harry smelled sulfur and brimstone from Hellfire. Someone used a Hellfire attack in Arctis Tor. The gateway they walked through was covered in charred bones and the courtyard next to it was covered in the bones of Mab's troll guard and goblins.

Small Favor
In Small Favor, Mab says that she and the Archangel Uriel had a common enemy that day, that there was one among the Fallen who had to answer for the Hellfire attack on Arctis Tor. Harry remembers the silvery hand and infers that Mab means Black Council and Thorned Namshiel.

Cold Days
In Cold Days, Arctis Tor is shown as comprising a labyrinth of corridors. When Cat Sith guides Harry Dresden, he leads him in a labyrinth of corridors made of green- and blue-hued crystalline ice, using, when needed, phosphorescent paw prints to mark the way. The hall where Harry's birthday was celebrated is a recreation of his Harry Dresden's apartment, in a scale of 1 to 8.