'Game Of Thrones' Season 5, Episode 5 Review
In "Game of Thrones" Season 5, episode 5, titled "Kill the Boy," Tyrion and Jorah head to Valyria. HBO

"Game of Thrones" Season 5, episode 5, "Kill the Boy," included a trip to Valyria, a place only mentioned in George R.R. Martin's "A Song of Ice and Fire" series of novels. Jorah and Tyrion also had a close encounter with the Stone Men. While the disease greyscale has been mentioned in the series, this was our first look at the exiled individuals who have it. Keeping up with the general theme of the season, "Game of Thrones" continued to forge its own path away from "ASOIAF." Here's everything you need to know about Valyria, the Doom and the Stone Men.

Warning: "Game of Thrones" Season 5 spoilers ahead.

The Doom Of Valyria

Much of the greatness of this empire has been lost. Its history is sprinkled throughout "Game of Thrones" -- Valyrian steel, Targaryens and dragons -- but the Valyrian Freehold has remained in the background. In the fifth episode of "Game of Thrones" Season 5, viewers were rewarded with a trip to Valyria. This is a place that author Martin only mentions, so it's a pretty big departure for the show -- although not quite the radical leap of last year's journey to the White Walker city.

The empire was once home to House Celtigar, House Velaryan and House Targaryen. The first two Houses never rose in power and currently pledge their loyalty to Dragonstone and Stannis Baratheon. Aegon the Conqueror, flanked by Rhaenys and Visenya, conquered Westeros -- except Dorne -- a century after the Doom of Valyria destroyed the Freehold. The catastrophic event that led to the destruction of the city is unclear, other than that it triggered earthquakes and volcanic eruptions to create various islands. Valyria was once home to 40 Dragonlord houses vying for power. Each of these noble families had dragons that they controlled, but only the Targaryens escaped Valyria with them.

The Targaryens left Valyria before the Doom due to a prophetic vision and established Dragonstone. After the Doom, the ruins of Valyria were believed to be haunted and no one traveled to them and made it back alive. In "ASOIAF," the ruins include the Fourteen Flames -- a volcano chain that remains active -- and the Smoking Sea. Euron Greyjoy said he traveled to Valyria and returned with Dragonbinder, which could be used to tame them.

Valyria doesn't seem as deadly in "Game of Thrones," but it's still a treacherous place. While the ruins are haunted by the Doom in the books, the Stone Men haunt Valyria on the show.

Greyscale And The Stone Men

Shireen has served as our introduction to greyscale in "Game of Thrones." The disease leaves the skin scarred and hardened and is usually fatal. Shireen survived due to treatment she received as an infant. People who have contracted the disease are known as Stone Men and are sent to outcast colonies. In "ASOIAF," the Stone Men were sent to the Sorrows, located off of the Rhone. "Game of Thrones" condenses Tyrion's story a bit, and Jorah contracts the disease after the encounter with the Stone Men.

Discussion

-- Tyrion mentions a dragon horn in passing, and I wonder if the duo will find one during their journey through Valyria. This could help establish Tyrion as one of the three people who will ride Daenerys' dragons and avoid the reveal of a secret Targaryen on "Game of Thrones." For fans of the R+L = J theory, we already know the two other riders.

-- "Game of Thrones" Season 5 is adding some elements of what happened to Jon Connington to Jorah's storyline, which could lead to some doubts about Young Griff. There has been no discussion of Euron either, and the Greyjoys remain on the sidelines for now.