Ch'Vyalthan

Ch&#39;Vyalthan, is an unseen character mentioned in the second season. He is deceased when the events of the series begin and is not expected to appear in the series. He was an Archmaester of the Citadel and the author of the book A History of the Great Sieges of Westeros.

Season 2
Tyrion Lannister refers to his book when preparing the defence of King's Landing. Varys criticizes him as a boring writer.