Lord Nathaniel Arryn holds regency of the Vale until his brother's son, Theon Arryn, comes of age. He served as Damon Lannister's Hand and later the Hand of the Crown, but returned to the Vale after his wife's suicide.
Nathaniel of House Arryn is the second born son of Lord Rumar Arryn and Lady Alyane Arryn. He served briefly as Master of Arms of The Vale for his brother, James Arryn, while the man ruled as Lord Paramount.
Nathaniel showed promise with a blade from a young age and became an excellent swordsman. His true gift, however, was his mind for military tactics which made him an excellent commander. During his time as Master of Arms in The Vale, he earned a reputation for dispensing justice harshly, but he saw himself as nothing more than an agent of the King's peace.
At the age of eighteen, Nathaniel fell in love with a smallfolk woman named Catelyn, though the romance was doomed. When Lord Rumar Arryn discovered his son's affair, he banished Catelyn and her family from the Vale. Nathaniel was informed years later that Catelyn had given birth to his daughter, Mya Rivers.
Near the beginning of the first era James Arryn was poisoned, an act attributed to Emmon Baelish during the Tourney at Harrenhal, but one which was actually planned by Rymar Royce. The lord's death left his infant son, Theon, as heir to The Vale, and Nathaniel took the position of Lord Protector of the Vale for his nephew. When the Lannisters made their bid for the throne, Nathaniel supported the usurpers, fighting alongside King Damon Lannister during the Battle of the Kingswood and accepting the position of Master of Laws for the Iron Throne following the Ascent of the Lion. House Arryn was the first of the Great Houses of Westeros to bad House Lannister.
After the fall of the Stag, Nathaniel married Alyce Connington at Storm's End during the Winged Wedding, a pairing that brought House Arryn closer to the new Lord Paramounts of the Stormlands.
After receiving permission from the Small Council, Nate set out to find Orys Connington who was assumed to have been captured by outlaws. He found the Stormlord being held by the former Lord Spirtual, Laenor Velaryon. After a brief exchange between the two, during which Laenor revealed that it had been Hand of the King, Loren Lannister, who had maimed the man's face and sent him to the Wall, Nathaniel exchanged Orys for a large gold reward, most of which was recovered during a subsequent ambush of Laenor's men.
Nathaniel departed for The Eyrie soon after returning to King's Landing, where he ordered Emmon Baelish thrown from the Moon Doors in retrubution for the murder of his brother. He then presided over The Grand Tournament of The Eyrie, held on the valley floor of The GIant's Lance.
Shortly after arriving back at King's Landing, Nathaniel's wife Alyce gave birth to their first child, Shiera Arryn. Following the death of Loren Lannister, Nathaniel was named the new Hand of The King, and his family moved into the Tower of The Hand. The Tournament of the Hand was held in honor of his appointment in 502 AC.
To protect his family from the threat of dragon fire after Queen Danae's flight, Nathaniel sent them from King's Landing to the safety of The Eyrie, though under the guise of protecting them from the War of the False King. Nathaniel remained in King's Landing, and was soon informed by Damon that, should he die during the war, the King intended the throne to pass to Nathaniel.
After the war's conclusion, Nathaniel became the Hand of the Crown. When his wife Alyce threw herself from the moon door, he struggled to fulfill his duties adequately, raising the ire of Queen Danae Targaryen, who urged King Damon to dismiss him. Nathaniel left King's Landing to return home, and Lord Aemon Estermont replaced him as Hand of the Crown.
Nathaniel ordered Bronze Gauntlet's campaign in the Mountains ended, as it became apparent that the costs of a prolonged fight would outstrip the befits gained. Soon after, as Nathaniel attempted to fulfill the betrothal between his sister Elyssa and Lord Ronnel Royce, she revealed that she was no longer a maiden to the attendees, in an attempt to antagonize him. These events led to a rocky relationship between Arryn and Royce, and coupled with Nathaniel suspicions that Lord Marwyn Belmore was actively acting against him, fueled Nathaniel's growing paranoia of his fellow Valemen.
Nathaniel reestablished the knightly order, the Brotherhood of the Winged Knights, charged with the protection of his nephew, Theon Arryn, as well as the rest of their House.
The Arryns relocated to the Gates of the Moon for Winter. Word of rebellion in the Three Sisters reached Nathaniel soon after. He used this as an opportunity to instruct his nephew in the ways of lordship as well as introduce him to his vassals properly as the Lord of the Eyrie.
In the Sacking of Sisterton, Nathaniel led the assault of the knights of the Vale alongside Ser Alester Templeton until being grievously injured just outside the town's walls by a young sistermen boy. Following the sacking, he was put under the care of Breakwater castle's maester and his armies healers. They concurred he needed to remain under ilk of the poppy to heal, after discovering his injury was not healing properly.
" Lord Arryn is as honorable as a Stark, and as stubborn as a Tully." - Damon Lannister
"... So they called in the cruel brother, The Falcon most grim, the justice, the cold one, to rule then for him!..." - Beren Merryweather, singing about Nathaniel Arryn
"I have 35,000 men outside your castle Baelish. I suggest you submit to Damon now, else we will come in and bend your knee for you" - Nathaniel's letter to Marq Baelish during the war