Runestone is a castle in the Vale of Arryn. It is the seat of House Royce, an ancient House once ruled the Vale as the "Bronze Kings" of the Vale before the Andal Invasion. House Royce are now one of the major vassal houses holding fealty to House Arryn of the Eyrie. The castle is located east of the Eyrie, on the coast of the Narrow Sea. It is north of the city port of Gulltown.
Robin Arryn is sent to be fostered at Runestone, where Royce's men begin attempting to train him to use a sword, but he is miserably bad at it. Sweetrobin was over-sheltered by his mother for years, and has never swung a sword before - unlike most boys who are even younger than the 13 year old Arryn boy. Petyr Baelish and his ward "Alayne" observe Sweetrobin tripping over himself in a practice yard, along with Yohn Royce. As Littlefinger and Alayne depart, Lord Royce promises that he will keep the boy safe, though he cannot promise his swordsmanship will improve.
In the novelsEdit
In the A Song of Ice and Fire novels, House Royce proudly descends from the First Men, one of the very few of their Houses to survive the Andal invasion in the Vale. The current head of House Royce wears ceremonial bronze armor covered in the rune symbols of the Old Tongue of the First Men, which are also featured on House Royce's sigil. It seems probable that "Rune-stone" was named after runes left behind by the First Men in the area.
Though the Royces descend from the First Men, it hasn't been specifically stated what religion they follow. Given that many Royces are knights, and that a septon named Lucos is stationed there, it seems that the Royces converted to the Faith of the Seven at some point in history.