"Game of Thrones" Season 6, episode 5, used Bran Stark's warging for a history lesson on the Children of the Forest. Before Bran's journey beyond the Wall, they were thought to have been either just a legend or wiped out during the Andal Invasion. Through Bran's vision in "The Door," viewers also discovered that the Children of the Forest were responsible for unleashing a dangerous enemy upon Westeros.

Warning: "Game of Thrones" Season 6 spoilers ahead.

We now know the Children of the Forest created the White Walkers out of desperation. The First Men — the human inhabitants of Westeros — had crossed into the country from near Dorne around 12,000 years before Robert's Rebellion, according to Westeros.org. In George R.R. Martin's "A Song of Ice and Fire" series, the First Men destroyed the forests, including heart trees, that were sacred to the Children of the Forest. The Children of the Forest resisted, but could not overcome the First Men. The Pact at the Isle of Faces ended the drawn-out war. The Children of the Forest would keep the forests while the First Men would get the other lands. The First Men also promised to not destroy any additional weirwood trees. 

During this period of peace, the Long Night occurred. A long winter and darkness fell over Westeros. The White Walkers arrived during this period from the far north. The Children of the Forest and the First Men joined together to defeat the White Walkers. To protect themselves from future attacks, Bran the Builder constructed the Wall. The Children of the Forest would also provide obsidian daggers to the Night's Watch because these weapons were effective against the White Walkers.

The First Men and the Children of the Forest lived in peace until the Andal Invasion, approximately 4,000 years after the Pact. The Andals killed the Children of the Forest and burned down weirwoods. The Kings of Winter — the powerful houses of First Men in the North — fought off the Andals. The rest of Westeros was conquered by the Andals.

In "Game of Thrones" Season 6, episode 5, it was revealed that the Children of the Forest created the White Walkers in response to the invading humans. Bran and the Three-Eyed-Raven see what appears to be the creation of the first White Walker, the Night's King. It's a departure from Martin's history. As David Benioff explained in the "Inside the Episode" feature, it's tragic. It also highlights another important theme in "Game of Thrones" that no one is really innocent, even the seemingly pure Children of the Forest. The Children of the Forest lost control of their creation, and the White Walkers now pose a greater threat to Westeros. 

While having the Children of the Forest create the White Walkers helps ground the terrifying, undead enemy, it also eliminates some of their mystery. In Martin's timeline, the White Walkers suddenly appeared during the Long Night. The uncertain history, weapons, language and origin adds another layer of intrigue to the White Walkers. The lore of the White Walkers would be fascinating to explore if they were another race that developed independently from humans in the far north. With the White Walkers fully revealed in "Game of Thrones," it will be interesting to see how Martin develops the characters in the books, "A Song of Ice and Fire."