Red King

"But the greatest rival to Winterfell was always the Dreadfort, and my ancestors, the Red Kings of House Bolton. If tales can be belived, we fought from the Long Night until the Andals came."

- Roose Bolton

Red King was a title held by the head of House Bolton of the Dreadfort during the Age of Heroes.

History
Before the North was unified under House Stark, the Boltons ruled vast stretches of lands to the east of Winterfell, and styled themselves as the "Red Kings of the Dreadfort". During this time the Boltons were the greatest rival of the Starks, and waged war against them for centuries.