Ulf the White is the secondary antagonist of The Princess and the Queen, or, the Blacks and the Greens, a novella by George R. R. Martin and a spin-off of A Song of Ice and Fire.
During the Dance of the Dragons, Rhaenyra Targaryen tried to recruit dragonriders to her cause. Many on Dragonstone claimed Targaryen descent through the affairs of Targaryens, their Valyrian blood could enable them to ride dragons. Among them was a man-at-arms on Dragonstone, the drunken Ulf the White, also known as Ulf White or Ulf the Sot, due to his pale hair (a sign of the blood of Old Valyria) and drunkenness. Silverwing, the dragon of Good Queen Alysanne, Rhaenyra's great-grandmother, allowed Ulf to ride her.
Ulf fought at the Battle of the Gullet for the Blacks and was knighted for this. However, at the First Battle of Tumbleton he and another dragonrider, Hugh Hammer, defected to the Greens, helping to defeat the Black army. For this they became known as the Two Betrayers.
Rhaenyra's half-brother Aegon II was missing, his children were infants, his next brother Aemond had died in battle with Daemon Targaryen, and the youngest brother Prince Daeron the Daring was still a young man. Hugh therefore decided to become King himself, due to his dragon. Ulf meanwhile wanted Highgarden, the Capitol of the Reach, and all its lands. A conspiracy among the Green Commanders, known as the Caltrops, decided to kill the Two Betrayers, Daeron agreeing to the plot. Meanwhile Ulf enjoyed the pleasures of wine and flesh, and those who did not please him were fed to his dragon.
When Addam Velaryon launched the Second Battle of Tumbleton at night, taking the Greens by surprise, Hugh was killed by the Caltrops. Ulf slept beneath a Tavern table through the battle. On hearing Hugh was dead, Ulf made a claim for the throne.
The Caltrop Ser Hobert Hightower pretended to agree to Ulf's claim and brought two casks of wine. Ulf was suspicious of Hobert and asked him to taste the wine that Hobert offered him. Hobert took a glass of wine, swallowed it all, praised the taste and called for another. Satisfied, Ulf drunk three glasses, and fell asleep. It was a gentle poison, and he died peacefully an hour later. When Ulf lost consciousness, Hobert tried to vomit up the poison, but it was too late and he also perished.