Meryn Trant is a knight of House Trant and a character of A Song of Ice and Fire and it's adaptation Game of Thrones. He mostly appears as a minor character and a minor antagonist and is the quarternary antagonist of season 5 of Game of Thrones.
In the TV series he's played by Ian Beattie.
Ser Meryn is a member of House Trant, a family of the stormlands and vassal house to House Baratheon. He becomes a knight of King Robert's Kingsguard after Robert's Rebellion. He's a proud man and a successful tourney knight. However he's not a friendly person and always breaks a knight's sworn duty to defend the weak and the innocent without hesitance or question. Sansa says he's not concerned about it, indicating his lack of morality and compassion. He's considered sly and cruel and he's loyal to Cersei Lannister, according to Varys. He is also allegedly responsible for the death of Syrio Forel, the master swordsman who was last seen dueling Meryn in the Red Keep. When Joffrey Baratheon ascends to the Iron Throne, Meryn acts as his enforcer.
In season 5 Meryn Trant takes the place of a removed character from the books: Rafford "Raff the Sweetling", and takes Raff's liking of little girls as well. Rafford was one of Gregor Clegane's men, and the murderer of Lommy Greenhands (Polliver is still the one who takes Arya's sword). Later Rafford accompanies the Master of Coin Harys Swyft to Braavos. In the show Harys appeared only in season 1, and Mace Tyrell goes to Braavos instead of Storm's End to deal with Stannis Baratheon's garrison. Meryn Trant accompanies him. It is then revealed on this trip that Trant is a sadistic pedophile after he picks a child prostitute over three adult ones at the Braavosi brothel.
In the show version Trant soon meets his end graphically during one of his brutal sessions at the brothel. After beating three little girls for his own pleasure, he notices one of them is not reacting to the beatings he gives her. It is then revealed this girl is in fact Arya Stark in disguise, who then brutally murders him by stabbing his eyes and chest before slitting his throat, in order to avenge the death of her mentor, Syrio. In the book version Raff is killed by Arya in the same way he killed Lommy, while the Tickler got Meryn's death in the third book. Trant is alive and well in the capital in the books.