Ardyn Martell, also called Blackfang, is a recurring character in the second, third, fourth, fifth, and sixth seasons. He is an exiled member of House Martell of Dorne, and is the cousin of the Ruling Prince of Dorne, Doran Martell. He is the personal bodyguard, assassin, and enfocer of Lord Petyr "Littlefinger" Baelish.
During Robert's Rebellion, he betrayed House Martell for unknown reasons and sided with Tywin Lannister. He was present during the Sack of King's Landing and claims to have witnessed the rape and murder of his cousin Elia Martell. When the rebellion ended, King Robert Baratheon had Ardyn returned to Dorne to answer for his crimes. Prince Doran decided to have him sent to the Night's Watch. However, while on the Kingsroad en route to the Wall, the caravan he was on was attack by brigands. Ardyn was saved by a party lead by Petyr Baelish, who had just been named Master of Coin by King Robert. Owing Petyr a life debt, Ardyn became his bodyguard and personal assassin. During the War of the Five Kings, Ardyn also operated as an unofficial member of the Blackwatch.
The reasons Ardyn betrayed House Martell are unknown, though it is believed that he did it to gain power.
Ardyn participated in the Sack of King's Landing as one of Tywin Lannister's men, and claims to have witnessed the rape and murder of his cousin Elia Martell. According various sorces, including Oberyn Martell, Ardyn watched Gregor "The Mountain" Clegane rape Elia. Elia repetedly begged for Ardyn to help her, but Ardyn just stood there and watched with a grin on his face.
Ardyn was a participant in King Joffrey's nameday tourney and was supposed to fight Ser Dontos Hollard, which ultimately did not happen due to the fact that Ser Dontos showed up late to the tourney and was in no condition to fight due to being drunk.