House Uller of the Hellholt holds a stark keep in the deep Dornish desert, raised by Andal adventurers who came over the Red Mountains in the days of the Coming of the Andals and settled along the smoking waters of the Brimstone. The castle takes its name from an old crime: a feud-ridden lord once bid his rivals to a feast within the walls, barred the doors, and burned them where they sat. From that fire the Ullers blazoned their arms, a field of yellow over crimson divided by a rayonny line of rising flame, and from that fire the saying spread across Dorne that half the Ullers are half-mad and the other half are worse.
In Nymeria's War the Ullers cast their lot with the Martells against the old Yronwood power, and when the war was won Lord Uller stood briefly as the aged second husband of the warrior queen herself, between her first husband and Ser Davos Dayne. They held to Dorne as fiercely under the dragons. In the First Dornish War Lord Uthor Uller emptied the Hellholt and led Lord Harlan Tyrell's army into the sands, where the Reachmen vanished; not long after, Queen Rhaenys Targaryen and her dragon Meraxes both fell in the courtyard of the castle, and rumour said the queen lived long enough to be tortured by her hosts. During the Dragon's Wroth that followed, four consecutive Lords of the Hellholt were murdered for the price the Iron Throne set upon their heads, and still the keep did not bend.
By the time of A Game of Thrones the house is held by Lord Harmen Uller, who came to King's Landing in the train of Prince Oberyn Martell with his brother Ser Ulwyck and his natural daughter Ellaria Sand, Oberyn's paramour and the mother of four of the Sand Snakes. When Arianne Martell schemes to crown Myrcella Baratheon at the Hellholt itself, she counts the Ullers among her likeliest swords; later, locked in her tower at Sunspear, she weighs sending for Lord Harmen and rules it too dangerous a thing to do.