Lancel Lannister

Before the war, Lancel serves as a squire to Robert Baratheon, a post he shares with his cousin Tyrek. The king makes no secret of his contempt for two boys who can't even lace his armour properly, treating them with the same rough humour he reserves for almost everything except his wine.

During a hunt in the Kingswood, Lancel keeps the king's wineskins filled, and Robert drinks without restraint. When a boar gores him fatally, Ser Barristan Selmy recalls that detail to Eddard Stark, and Varys presses the squire on it: Lancel says it was Queen Cersei herself who handed him the skins, telling him it was her husband's favourite vintage.

With Jaime Lannister a captive in the north, Cersei turns to her young cousin for comfort, and the two become an open secret inside the Red Keep. The queen regent has Lancel knighted, and the newly made Ser Lancel becomes her constant companion.

Tyrion Lannister, acting Hand of the King, pulls at the thread of Robert's wine and finds that what Lancel served the king was stronger than Robert was used to. When Tyrion locks up Grand Maester Pycelle, it's an emboldened Lancel who comes demanding his release on Cersei's behalf — and Tyrion uses the moment to squeeze out a confession: Lancel's part in the king's death, and his affair with the queen. From then on he blackmails his cousin into spying on her.

Lancel survives the riot that breaks out in the streets of King's Landing, and rides back to the Red Keep at Cersei's side, with young Prince Tommen between them.

Lancel asks for a command of his own in the coming battle against Stannis Baratheon, and gets it. At the Blackwater he's wounded in the arm, and the sight of his bloodied surcoat is enough to set off screaming among the women sheltering in the Queen's Ballroom.

He objects when Cersei wants Joffrey pulled from the fighting and locked inside Maegor's Holdfast, fearing the king's disappearance will break the defenders' morale; Cersei answers by striking his wound open again. It's Sansa Stark who has him carried off to Maester Frenken. Tywin Lannister and Mace Tyrell arrive in time to crush Stannis's army.

As a reward, Lancel is granted the lordship of Darry, in the Riverlands. Cersei suspects the appointment is really her father's gesture toward Ser Kevan; for now, no one knows whether Lancel will keep his arm, or his life.

The wound won't close. It festers for months while Cersei prays at his bedside and Kevan Lannister tells Tyrion that his son has been praising the courage shown at the Blackwater. Tywin even considers marrying him to Sansa Stark, but Kevan doesn't think Lancel fit enough to consummate a marriage, so the match falls to Tyrion instead.

With Martyn a prisoner of Robb Stark and Lancel bedridden, House Lannister takes another blow: Lord Rickard Karstark kills the third brother, Willem. After the Red Wedding, Tywin decides Lancel will marry a Frey girl, sealing the alliance with Lord Walder Frey.

Kevan pulls him out of bed for the wedding feast of Joffrey Baratheon and Margaery Tyrell. Thin now, his hair brittle, Lancel is praised by Sansa for his courage, a compliment that makes father and son beam alike; they sit in places of honour near the Iron Throne when Joffrey chokes to death in front of everyone.

Maester Ballabar pulls him through, but Lancel emerges from the illness a changed man: he tells Cersei the High Septon prayed with him, and that he's found a new faith. Unsettled by what her cousin might confess, the queen tells him to pray silently instead.

After the siege of Riverrun, Ser Harwyn Plumm drives out the last men loyal to Darry's old lords, and Lancel rides there with his father and two septons, quartering the Darry ploughman with the Lannister lion on his new arms. He marries Amerei Frey, but the marriage is never consummated: Lancel sleeps in the castle sept, fasts, shaves his crown, and surrounds himself with sparrows and Warrior's Sons. Kevan eventually leaves Darry after a quarrel with his son.

When Jaime visits, he finds a barefoot, gaunt man who claims nightly visions of the Seven and finally admits to giving Robert the wine, and to sleeping with Cersei, whom he loved. Lancel announces he's giving up Darry and Amerei to join the High Sparrow and the Warrior's Sons; Jaime refuses his repeated requests to pray together. At Riverrun, the news stuns Daven Lannister, though not Genna.

Back in King's Landing, Lancel is among those who accuse Cersei before the Faith after her arrest. The imprisoned queen admits to the High Sparrow that she slept with him, though she denies plotting Robert's death with Lancel. When Cersei makes her walk of atonement through the city, Lancel rides in her escort, under Ser Theodan Wells.

Kevan, now Lord Regent to young King Tommen, considers naming his son to the Kingsguard, but before that happens Varys has him killed. In the books, Lancel is still alive at this point in the story; the show closes his arc earlier, placing his death in the year 303.