Ser Meryn Trant is a knight of the Kingsguard under King Robert Baratheon and subsequently Kings Joffrey and currently Tommen.
Ser Meryn Trant is a member of House Trant, a vassal house to House Baratheon. He becomes a knight of the Kingsguard of Robert Baratheon after Robert's Rebellion. He is a successful tourney knight, though Sandor Clegane is scornful of Trant's skills, remarking that "any boy whore with a sword could beat three Meryn Trants."
He takes great pride in his status as a knight of the Kingsguard, even though he routinely follows orders which break a knight's sworn duty to defend the weak and the innocent without hesitance or question.
Ser Meryn Trant is sent with a group of Lannister guardsmen to apprehend Arya Stark. Syrio Forel defends her, armed only with a wooden practice sword. He disables the Lannister guardsmen, to Meryn's fury and disbelief. Syrio tells Arya to run as he faces down the heavily-armored knight. Later, Ser Meryn stands amongst the other Kingsguard in the throne room. Syrio's fate is not mentioned.
Ser Meryn is present when Joffrey shows Sansa her father’s head on a spike, and she tells Joffrey that someday Robb may bring her Joffrey's head. As Joffrey says his mother has told him that a king should not strike a woman, he orders Ser Meryn to hit Sansa. Meryn shows no emotion as he does so.
Ser Meryn guards King Joffrey Baratheon during his Name Day Tournament in the Red Keep. When Ser Dontos Hollard arrives drunk for his bout Joffrey orders Meryn to pour a barrel of wine down Dontos' throat. Joffrey relents when he is told it is bad luck to kill a man on his name day by Sansa Stark, who convinces him to make Dontos his court fool instead.
Following Robb Stark's victory over Stafford Lannister at the Battle of Oxcross, King Joffrey has Sansa Stark brought to court to answer for her brother's crimes. He points a loaded crossbow at her and then commands Ser Meryn to beat Sansa but spare her face. Meryn punches Sansa hard in the stomach and then knocks her over using the flat side of his sword. Joffrey orders Sansa stripped and Meryn tears her dress from her shoulders. Sandor Clegane watches on in disgust at Trant's behavior.
Tyrion Lannister interrupts the assault on Sansa and asks Meryn what kind of knight beats a helpless girl; he answers with "the kind that serves their king". Bronn sarcastically warns Meryn to be careful of getting blood on his white cloak. Tyrion orders Sansa covered and reminds Joffrey that she is his betrothed. He rebukes Joffrey for absurdly punishing Sansa for events she had no part in. He also notes what became of the Mad King, who also did what he liked until he was killed by the King's uncle. Meryn warns Tyrion not to threaten the King; Tyrion counters that he is educating his nephew. He instructs Bronn to kill Meryn if he speaks again and points out that that is a real threat. Tyrion helps Sansa up and walks her out of the throne room.
Ser Meryn, along the rest of the Kingsguard, is present when Princess Myrcella Baratheon is sent to Dorne alongside her sworn shield and Meryn's sworn brother, Ser Arys Oakheart. When Joffrey provokes a riot, Ser Meryn cuts down several enraged smallfolk before bringing the King to safety. When Tyrion orders Ser Meryn to gather men to help rescue the missing Sansa Stark, he angrily replies that he takes his orders from the king and refuses to go, as Joffrey is too busy sulking and doesn't care if Sansa dies.
Ser Meryn and one of his sworn brothers accompany Cersei Lannister to her brother Tyrion's new chambers. They wait outside at Tyrion's insistence. When Bronn and Podrick Payne appear to see Tyrion, the two knights exchange barbs; Meryn is incredulous that Bronn has been appointed a knight for his efforts at the Battle of Blackwater. He sneers that Bronn is merely an upjumped cutthroat, while Bronn, more amused than offended by Meryn's comment, mocks Meryn for being better at "beating little girls than fighting real men", infuriating Meryn. Bronn tries to push past for his meeting with Tyrion, but Ser Meryn bars his way and threatens to cut off his hand if he tries to enter. The two Kingsguard begin to slowly draw their swords, unaware that Bronn also has the knife on his back half drawn. Before they can fight, Cersei reappears, and Ser Meryn leaves with her.
Ser Meryn is present alongside his fellow Kingsguard when Joffrey meets with his grandfather and Hand of the King, Tywin Lannister. Ser Meryn also attends Tyrion and Sansa's wedding ceremony along with Joffrey and the other Kingsguard.
Ser Meryn is present when Jaime Lannister is discussing placement of the Kingsguard during the wedding feast. Jaime is irked by Meryn's sycophantic agreement to Joffrey's bragging that he is responsible for keeping the people fed (Jaime notes that this is more the doing of the House Tyrell) and claiming he singlehandedly won the war. When Joffrey is poisoned at his wedding feast, Ser Meryn is among the Kingsguard who surround and apprehend Tyrion.
When Arya Stark tells Sandor Clegane that she believes Syrio Forel was killed by Meryn, Sandor refers to him as "Meryn fucking Trant" and comments "Any boy whore with a sword could beat three Meryn Trants".
Meryn also speaks as a witness at the trial of Tyrion Lannister. He tells the court how Tyrion slapped and insulted Joffrey during the Riot of King's Landing. Meryn also states how Tyrion compared Joffrey to the Mad King and threatened both of them. Tyrion tries to defend himself by stating he threatened Joffrey and Meryn because they were openly abusing Sansa Stark, but Tywin orders him to remain silent. Following Tyrion's outburst, Tywin orders Meryn to escort him back to his cell, but not before Tyrion demands a trial by combat.
After Tyrion's trial, Jaime berates his brother for his outburst and throwing his life away. While discussing the upcoming trial by combat, Tyrion believes that Bronn will fight for him just as he did at the Eyrie. Tyion hopes Cersei names Meryn Trant as the crown's champion, saying he would enjoy watching Bronn disembowel that "pompous child-beater". However, Jaime informs Tyrion that Ser Gregor Clegane has been named as the crown's champion.
Ser Meryn helps escort Cersei Lannister to the Great Sept of Baelor, where the funeral of Tywin Lannister takes place
Ever since Tyrion Lannister's escape, Cersei has offered a lordship to anyone who brings her the head of her younger brother. Meryn has brought two men who claim to have Tyrion's head and brings them before the queen, but Cersei reveals that they have killed the wrong dwarf, to Ser Meryn disgust, so he suggests imprisoning them. However, the Queen pardons the men, as imprisoning them might dissuade other hunters
Ser Meryn accompanies Cersei when she visits the High Sparrow. Although he voices his concern about such a visit, Cersei believes that the Sparrows are deeply religious and that they are in no danger
When Mace Tyrell is assigned to negotiate a deal concerning the Crown's debt with the Iron Bank of Braavos, Cersei assigns Ser Meryn to escort Mace to Braavos
Ser Meryn Trant arrives in Braavos as an escort of Mace Tyrell flanked by some Lannister soldiers. He is spotted by Arya Stark who recognizes him immediately. Taking some time off, Meryn and his Lannister men enter a brothel. Ser Meryn is offered multiple prostitutes but he declines them all for being too old until a very young girl is offered
The next night, Meryn beats three girls to the point of tears for his own pleasure, though only the first two cry. The third does not show any signs of weakness, and he orders the first two out of the room. As he steps closer, he is shocked as the girl removes her face and reveals herself to be Arya Stark. He is stabbed in both eyes and several times in the chest. Arya toys with him by stabbing him several more times and mocking him as he is left whimpering from the pain, until she finally slits his throat.
One of Joffrey's most loyal Kingsguards, Ser Meryn took care of much of Joffre's dirty work. His devotion to the late king put him at odds with Tyrion Lannister, and he was the first to testify against Tyrion when he stood trial for Joffrey's murder. Meryn Trant was killed in Braavos by Arya Stark who held him responsible for the death of her teacher Syrio Forel.