The lead pyromancer Hallyne is portrayed by Roy Dotrice, who passed away in 2017, and was a long-time personal friend of author George R.R. Martin. He also narrated the audiobook editions of the novels. Dotrice was originally cast as Pycelle, but had to withdraw due to health problems. He was replaced by Julian Glover, who had worked with Dotrice before.
In Stannis and Renly's tents there are tapestries hanging depicting battle scenes. These are sections taken from the so called Bayeux Tapestry, which depicts the Battle of Hastings, the key battle of the Norman conquest of Britain, where English King Harald died fighting the invader William, Duke of Normandy, later known as William the Conqueror.
The episode title refers to a phrase used in the novel "A Clash of Kings" where the Lannister troops attribute the mysterious murders perpetrated by Jaqen H'ghar to a ghost that resides in the cursed ruins of Harrenhal. Arya then uses the term several times to describe herself during her time in Harrenhal, since she is the one initiating the murders. The phrase is not used in the TV episode, however.
Jaqen H'ghar states that he owes the Red God three deaths that were stolen from him. The Red God is another name for R'hllor, better known as the Lord of Light or the Fire God.
The episode won an Emmy Award for outstanding art direction for a single-camera series.