Daeron Targaryen finally made his debut in 'House of the Dragon.' Here's what to know about Alicent's youngest son.

• In "House of the Dragon," Daeron Targaryen is the youngest son of Alicent and the late King Viserys.
• Daeron grew up with the Hightowers in Oldtown, rather than in King's Landing with his siblings.
• He finally makes his debut in "HOTD" season three. Here's what to know about Daeron in the book.

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

The elusive Daeron Targaryen is finally joining the fray in "House of the Dragon."

Daeron is the youngest son of Alicent Hightower and the late King Viserys Targaryen — their fourthborn child after Aegon, Helaena, and Aemond. Like his siblings, Daeron is a dragonrider, bonded to a young blue dragon named Tessarion.

Unlike his siblings, however, Daeron left King's Landing as an infant. He was sent as a ward to Oldtown, the seat of House Hightower, and is scarcely known to the royal family. Throughout the first two seasons of the HBO show, Daeron is kept far away from the action.

In "House of the Dragon" season two, Daeron is mentioned as both a potential threat to his half-sister, Queen Rhaenyra Targaryen, and a promising pawn in Aegon's army — especially once Tessarion has grown big enough to fly into battle. Daeron is also mentioned in a conversation between his mother and uncle, Ser Gwayne Hightower (Freddie Fox), who was also raised in Oldtown.

Gwayne tells Alicent that 16-year-old Daeron is hardworking, clever, and kind, setting him apart from his cruel, bloodthirsty brothers.

In season three, Daeron finally makes his onscreen debut, marching with the Hightower army and taking orders from his mother's cousin, Lord Ormund Hightower (James Norton) — that is, until episode three, when their campaign is interrupted by Daemon Targaryen (Matt Smith). Now that Rhaenyra has ascended the Iron Throne, the king consort plans to take Daeron hostage as part of the Hightowers' surrender terms.

"It would be rather an oversight to allow one of Prince Aegon's heirs to go prancing about the Reach with his dragon, no less," Daemon tells Ormund. "We will treat him kindly, as we would any son of Viserys. As long as you behave yourself."

By the end of episode three, viewers discover that Ormund has deceived Daemon and Rhaenyra, delivering a faux-blonde imposter to be taken hostage and keeping the real Daeron by his side.

As showrunner Ryan Condal previously confirmed, Daeron will have a role to play in the ongoing civil war — but if you're impatient to learn why Daeron might become important in "House of the Dragon," keep reading to find out what happens to him in the original book, "Fire & Blood."

Daeron, the most well-liked of Alicent's sons, becomes a great threat to Rhaenyra's reign

According to "Fire & Blood," Alicent gives birth to Daeron around the same time that Rhaenyra gives birth to her first child, Jacaerys, and he enters the Dance of the Dragons at age 15.

Daeron is described in the book as "gentle and soft-spoken," the most charming and well-liked of Alicent's sons. His "lovely blue she-dragon," Tessarion, is known as the "Blue Queen."

When Ormund is overwhelmed at the Battle of the Honeywine, Daeron saves him by swooping in with Tessarion. They snatch an unlikely victory, leading Ormund to knight him "Ser Daeron the Daring."

Led by Ormund on foot and Daemon on dragonback, the Hightower army continues to win victories throughout the Reach, mostly by using Tessarion to force surrenders. While they advance on King's Landing, Prince Daeron the Daring comes to be known as the greatest threat to Rhaenyra's reign, "smashing the queen's loyalists" and "forcing every lord who bent the knee to add their strength to his own."

Eventually, Rhaenyra decides to send two of her dragonseeds, Ulf White and Hugh Hammer (bonded to Silverwing and Vermithor, respectively), to end Daeron's campaign. The duo flies to Tumbleton, a town southwest of King's Landing — the last stronghold that lies between the Hightower army and the city — with orders to kill Daeron and Tessarion when they arrive.

Daeron's fate is tied to the Treasons of Tumbleton

Once Daeron arrives in Tumbleton, Ulf and Hugh decide to switch sides.

In what comes to be known as the Treasons of Tumbleton, the bastards-turned-dragonriders betray Rhaenyra and join the Hightower host. The book doesn't give a definitive answer as to why: "It may be that it was the thought of attacking Tessarion that gave them pause," it reads, "though both Vermithor and Silverwing were older and larger than Prince Daeron's dragon, and would therefore have been more likely to prevail in any battle."

"Others suggest it was avarice, not cowardice, that led White and Hammer to betrayal," the book continues. "Honor meant little and less to them; it was wealth and power they lusted for."

Indeed, Ulf and Hugh were knighted after the Battle of the Gullet and the fall of King's Landing, but both had hoped for lordship or castles to call their own. It seems they grew dissatisfied with Rhaenyra's rewards while emboldened by their own powerful dragons. Targaryen history books immortalize them as the Two Betrayers.

Ormund dies in the ensuing battle, slain by the Northern soldier known as Roddy the Ruin, but Daeron survives.

Daeron remains in Tumbleton as the town devolves into violence and chaos. Despite his prowess on dragonback, Daeron is too young and inexperienced to assume Ormund's leadership role, and he fails to stop his soldiers from pillaging.

Eventually, Addam Velaryon (previously Addam of Hull) flies to Tumbleton on his own dragon, Seasmoke, determined to retake the city from the Two Betrayers and "to prove that not all bastards need be turncloaks."

The book says that Daeron is asleep in his tent when the attack begins. Some sources say he died in the flames, while others claim he briefly escaped before he was cut down, either by a sellsword or other unknown man-at-arms. Either way, Daeron dies in the Second Battle of Tumbleton.

Tessarion also fights Seasmoke and Vermithor, and all three dragons die as a result. Addam and Hugh also die in the battle.

Ayomikun Adekaiyero and Palmer Haasch contributed to a previous version of this story.