Faerie Courts

The Sidhe Courts (Summer and Winter) are the two ruling bodies of the Sidhe and their lands make up most of the Nevernever. Their combined power can affect the real world through the barrier of the Nevernever, and maintaining the balance of power is greatly important to most members of the supernatural community. It supposedly is responsible for the continued cycle of the seasons, and is rumored that great ecological disasters such as Ice Ages and Global Warming were caused by imbalances between the two Sidhe courts.
Each court is ruled by three Queens—Queen Mother (neither of whom have been given a name outside of their title of Mother Summer and Mother Winter), Queen, and Lady. Bob refers to the three as "The Queen Who Was," "The Queen Who Is," and "The Queen Who Is To Come" respectively. They are forbidden from taking hostile action against mortals without their consent—such as making a deal with one of the Sidhe. However, each court has a Knight, a mortal champion appointed by a Queen, who may involve him or herself in mortal affairs.
Sidhe cannot tell a direct lie, but instead are masters of twisting words in order to convey falsehoods without actually lying. They are strictly concerned with the wording rather than the intent of agreements and will specifically place loopholes in agreements which they can exploit. In almost every case, a mortal making a deal with a Sidhe will end up causing the mortal to get the short end of the stick with any attempts to withdraw from the deal causing the mortal to become further involved with the Sidhe. Sidhe are also vulnerable to cold iron. This weakness also extends to any form or alloy of iron, such as steel blades or iron nails. The Knight of each court does not share these weaknesses, although it is hypothesized that iron or steel may bypass certain defenses or magics used by the Knight, those magics being Sidhe in origin.
The two sides are engaged in a Cold War, in which both sides are mobilized for battle but never engage in anything more than skirmishes. Large battles between the two courts have great effects in nature including weather patterns, and are usually avoided unless there is no other choice such as in the events of the novel Summer Knight. Each side is stronger during their namesake season, with the balance of power shifting during the Summer and Winter Solstices. Despite their ongoing conflict, both Queen Mothers live together seemingly peacefully in a cottage. Also, members from both courts have worked together, most recently the Winter Lady and Summer Lady in the events of the novel Proven Guilty.
The Sidhe exchange control of an artifact called the Stone Table twice a year at Midsummer and Midwinter. Whichever Court is in control of the Table steadily gains in power, and in order to preserve the balance, the Summer Court hand it over at Midsummer, the height of their strength, and the Winter Court hand it over at Midwinter, the height of their strength. The power of any being killed upon the Stone Table goes instantly to the court which is currently in possession of it.