The Winter Court is the domain of the Cold Boy. It is the eldritch dimension where the Children of the Cold live and use to travel. At first, it may just look like an ordinary city with snow and ice everywhere, but soon it becomes different. All the buildings are made of ice and are intricate structures except for one, however: the Winter's Heart where you can see the "true" form of the Cold Boy.
All the Children of the Cold have seen it only once - and it turns their eyes black and begins the process of their becoming numb/dead.