Serwyn Errol

Ser Serwyn Errol is an unseen character in Game of Thrones. He is not expected to appear in the series, being long dead by the time it starts.

Biography
Serwyn is mentioned in the book The Lineages and Histories of the Great Houses of the Seven Kingdoms. He was Lord Commander of the Kingsguard during the reign of King Aenys Targaryen and knighted Raymont Baratheon.

Reference

 * A Golden Crown