House Bolton of the Dreadfort is a Great House from the North. Their original lands were in the northeast of the Stark territories. Their stronghold was a castle called the Dreadfort and the head of the house was the Lord of the Dreadfort.
House Bolton was infamous for its centuries-old practice of flaying their enemies alive, to the point that they used a flayed man as their House sigil. The Boltons supposedly gave up this practice after bending the knee to House Stark, and centuries later Lord Eddard Stark outlawed flaying in the North altogether, but the Boltons continued the practice in secret. This resulted in them being despised and feared by many of the Northern houses, especially after their betrayal of House Stark and their torching of Winterfell.
After the events of the Red Wedding, House Bolton was appointed the new Great House of the North, having usurped their position from their former liege lords, House Stark. Lord Roose Bolton became the new Warden of the North.
House Bolton's heraldry consists of a red flayed man upside-down on an x-shaped white cross over a field of black. Their house words are "Our Blades Are Sharp," though a common saying of members of the house was "A naked man has few secrets; a flayed man, none."