'House of the Dragon' just introduced a big-mouthed new character — but he's probably going to be important later on

"House of the Dragon" introduced Ulf as a tavern patron who claims to be a Targaryen descendant. He's an important character in "Fire and Blood."

• "House of the Dragon" introduced Ulf, a common man who claims to be a Targaryen bastard.
• His claim may have merit — in "Fire and Blood," he proves to be a pivotal character.
• Here's who Ulf is in "Fire and Blood," and what happens to him in the book. 

Warning: Spoilers ahead for "House of the Dragon" season two, episode three, and the book "Fire and Blood."

This week's episode of "House of the Dragon" took a brief detour into the seedier parts of King's Landing — and in the process, it introduced us to yet another character who will likely serve a pivotal role later in the series.

Season two, episode three, titled "The Burning Mill," briefly spotlighted a cheery bar patron, Ulf. After working the room a bit, Ulf settles down at a table and almost immediately claims to a stranger he's a Targaryen descendant.

While it'd be easy to dismiss Ulf's claim as drunken hearsay, there's probably some merit to it. We're probably going to be seeing a lot more of Ulf in "House of the Dragon," depending on how closely it follows "Fire and Blood," George R.R. Martin's history of Westeros.

If you're not keen on spoilers for "Fire or Blood," or the potential future of "House of the Dragon," best not to read ahead.

Ulf claims to be the son of Baelon the Brave, and thereby a descendant of King Jaehaerys

At the tavern, Ulf meets a Dornish man and remarks that Dorne was one part of Westeros that his house never conquered. When pressed, he plays coy, and then lets slip that King Jaehaerys was his grandsire. His father, he says, was Baelon the Brave, making Ulf the illegitimate brother of Daemon Targaryen and King Viserys.

Ulf also refers to Rhaenyra — his niece, if his claims are to be believed — as the "one true queen," a dangerous move in the Aegon II-controlled King's Landing.

"The blood of the dragon runs through these veins, and yes, men would take my head for it," Ulf says. "A Dragonseed must watch his own neck when he has no white-cloaked guardsmen to do it for him."

Ulf eventually shuts up after saying that his "nephew," Prince Jacaerys Velaryon, is the rightful heir to the Iron Throne. Coincidentally, that's the moment that Aegon II walks in with his entourage — and Ulf is quick to call out an "All hail the King!"

Ulf becomes a dragon rider in 'Fire and Blood'

In "Fire and Blood," Prince Jacaerys issues a challenge in a bid to make use of the unclaimed dragons during the war: Any man able to successfully mount a dragon without a master would be richly rewarded. Some of those men were "seeds" — bastards who had Targaryen blood in their veins.

Ulf successfully bonded with Silverwing, the former mount of Queen Alysanne, the sister and wife of King Jaehaerys. During that time, he was referred to as "Ulf the White" or "Ulf the Sot," referencing his white hair and drinking habit. Eventually, he came to be known as Ulf White.

Ulf fought alongside other dragon riders like Hugh Hammer in the Battle of the Gullet, a pivotal sea battle during the war. "Fire and Blood," citing the historical record left by the dwarf Mushroom, recounts that both Hugh and Ulf celebrated after the violent battle, with Ulf declaring that they should become lords.

Ulf and Hugh were several times denied entry into nobility. Rhaenyra shut down a potential marriage between Ulf and the daughter of Lord Stokeworth, after killing the lord for betraying her. She also denied Daemon's proposal of granting Storm's End, the seat of House Baratheon, to Ulf, after the Baratheons sided with Aegon II during the war.

In the book, Ulf and Hugh betrayed Rhaenyra

During the war, Ulf, Hugh, and their dragons Silverwing and Vermithor, were sent to the town of Tumbleton to defend it from Lord Ormund Hightower, who was advancing toward King's Landing. During the battle, however, the two defected and attacked the town instead.

According to Mushroom's historical account in "Fire and Blood," Ulf descended into hedonism, raping multiple women in Tumbleton each night and constantly drinking. Though Prince Daeron, Alicent and King Viserys' youngest son, had named him the Lord of Bitterbridge, he coveted Highgarden, the seat of House Tyrell. He and Hugh refused to advance on King's Landing until they were rewarded sufficiently, and the lords under Prince Daeron conspired to kill them.

But the fight came to Tumbleton when Addam Velaryon (previously Addam of Hull), another dragon rider, attacked the city on his dragon Seasmoke. Ulf was drunk and asleep during the battle, during which Hugh, Daeron, and Addam all died. When he awoke, he agreed to march on King's Landing, and said that he should be instilled on the throne after they conquered it.

Shortly after, Hobert Hightower killed Ulf — and in the process, himself — through a poisoned cask of wine.

"House of the Dragon" season two airs Sundays at 9 p.m. ET on HBO and is streaming on Max.