Youngest of 4 sons, Martyn Dayne had little chance of inheriting Starfall. His older twin brothers both abdicated to avoid a succession crisis, leaving the seat of Starfall to Ulrich Dayne. Neither of them had proven to be worthy of wielding the greatsword Dawn, and this was passed to Ulrich as well when he was deemed worthy. However, Ulrich's prowess with the blade led him to become part of the Kingsguard, leaving Starfall to young Martyn Dayne, at that point in time age 20. His mother died giving birth to him, and his father remarried after several years, resulting in Martyn's 2 younger sisters Arianne Dayne and Ashara Dayne.
As is traditional, Martyn spent his earliest years in the Water Gardens. When he reached age 10, he returned to Starfall. As he was not expected to become Lord of Starfall, Martyn was free to do as he please. He chose to do what Edric Dayne had done 200 years ago, and travelled through Westeros as a page, and later squire, to Ser Borin Blackmont. He returned to Dorne eight years later, a man.
His eyes are a deep purple and his hair is wavy and blonde, bordering on white. He is slim of build with toned muscles, his face mirrors this and is angular with sharp cheekbones. His skin is tanned, but considered fair when compared to the typical Dornishman, a trait shared by most of the Dayne bloodline. He stands at 5'7, making him shorter than most Westerosi.
Martyn Dayne participated in the Tournament at Harrenhal, losing in the joust to Damon Lannister. He participated in the Battle of the Rainwood, and afterwards obtained a new castle forged steel sword.
He returned to Dorne and travelled to Sunspear, where he met Princess Sarella Martell. The two formed a close bond when he began offering her lessons with a spear as an excuse to spend more time with her.
When the Lannisters took the throne and Sarella rose to become Lady of Sunspear, Martyn urged the Dornish lords at her war council to push for Dornish independence. He and Sarella were then betrothed, but he left Sunspear shortly thereafter in order to fight alongside his brother Ulrich Dayne in leading a rebellion against the Lannisters at Stonehelm. In the battle, Martyn was taken prisoner and held hostage in order to force a surrender from Ser Ulrich. Afterwards, the two brothers were taken back to the capital as prisoners.
Princess Sarella negotiated for the release of the two Dayne brothers. King Damon agreed to their safe return, but under the guise of a trial by combat in order to not appear concessionary. The two rulers agreed to have Martyn Dayne face an easy opponent in order to win his freedom, however Lord Varyo Velaryon chose a vicious champion, Maidensblood, due to his hatred for Ser Ulrich. Martyn managed to win the fight with difficulty, but recieved a rather severe wound. After he recovered, he returned to Sunspear.
Martyn wed Sarella Martell at the start of the second era. During the wedding feast, Ser Ulrich confessed that he had been a paramour the Princess, and told him that Sarella had also slept with Damon Lannister. Ser Ulrich then fled, leaving Martyn to confront Sarella. The two made amends after some time, and Sarella soon announced a pregnancy after they returned from a visit to the Reach.
Near the end of the era, after his wife agreed to ally with Prince of Lys against the Sealord of Braavos; he led a Dornish host to Essos to join with Prince Varyo's forces. Martyn fought against the Braavosi on the plains of Vasugys on the Orange Coast.
Martyn became consumed with feelings of jealousy and hatred towards his brother, Ulrich Dayne, who was imprisoned for breaking his oaths. After being manipulated by Damon Lannister with lies and doubts about Prince Lewyn's true father, Martyn regrettably killed Ulrich in a trial by combat.
Martyn spent some time alone in Essos before returning to Sunspear and his wife.
Martyn traveled to King's Landing once more in order to swear fealty (alongside his wife) to the new diarchy of House Lannister Targaryen.
In order to maintain House Dayne's future, Sarella revoked Martyn of his title as Lord of Starfall, in favour of his sister, Arianne Dayne.
After finding out about her affair with Andrey Martell, Sarella had her former lover, Ellaria Uller, killed. Martyn, along with Aero Allyrion, were the first to find her body, and to find out about the incident. Martyn would then go on a personal mission to find out the truth behind this, resulting in him making the decision to leave Sunspear.
“The Prince is a Dayne of Starfall, Lord of his ancient seat and head of the house that holds Dawn. He has loftier concerns than who shares his lover’s bed.” - Sarella Martell
Sarella Martell, wife
Lewyn Martell, son
Tyene Martell, daughter
Arthur Dayne, father (deceased)
Cailin Dayne, brother
Jon Dayne, brother
Arianne Dayne, sister
Ulrich Dayne, brother (deceased)
Ashara Dayne, sister
Jenna Dayne, aunt