Theon Greyjoy

Theon Greyjoy is a major character in Game of Thrones. He is played by Alfie Allen and debuts in the first episode.

Theon is the son and heir of Lord Balon Greyjoy, the ruler of the Iron Islands. Some years ago, the Iron Islands rose in rebellion against the Iron Throne and were crushed in a war led by King Robert Baratheon and Lord Eddard Stark. The ironborn surrendered and Balon was allowed to remain overlord of the isles in return for his only surviving son Theon being given as a hostage and ward to Eddard Stark. Despite his status as a hostage, Theon has nevertheless been treated well by the Starks.

In the books
In the Song of Ice and Fire novels, Theon was a young boy when the rebellion was crushed and his two brothers were killed. He has been raised at Winterfell for the nine years since and has become close friends with Robb Stark. He is cordial to the rest of the family, but more distant. Theon is known for his arrogance, as he is the heir to one of the Great Houses of Westeros, despite not having seen home in a long time.