Winter Court (Unseelie)

The Winter Court is colder and much more merciless than its Summer counterpart. The lands of Winter resemble a tundra or frozen wasteland, with the center being Arctis Tor, a massive fortress made of black ice. Some of the lesser creatures of Winter include trolls, goblins and fetches, spirits which feed on the fear of others.
The Winter Queen and Winter Lady throughout the series to date have been Mab and Maeve respectively. Lloyd Slate, the Winter Knight was revealed as a traitor during the events of Summer Knight and was subsequently subjected to repeated tortures by Mab. Eventually, during the events of Changes, Slate was killed and replaced as Winter Knight by Harry Dresden. Harry's godmother, the Leanansidhe, is also a very powerful member of the Winter Court. The Erlking, the leader of the Goblins and the Wild Hunt, also has some manner of relationship with the Winter Court and Mab, although he is not a vassal.
Harry currently owes Queen Mab one more 'favor' in order to free himself from his obligation to the Sidhe, although Mab has mentioned that by taking up the Mantle of Winter Knight, Harry has freed himself of any previous obligations to her. Three times she has asked Harry to take up the mantle of Winter Knight, which Harry has refused because (among other reasons) a Winter Knight can only abandon their title through death. Recent events have suggested that Queen Mab may be going insane which is causing a great deal of uneasiness among the sidhe and magical community. It is possibly due to the gift that she took from the Leanansidhe, Harry's Faerie Godmother, although Mab herself describes it as simply rage against those who would dare strike at her (likely meaning the Black Council and all its allies and pawns).