Since the beginning of "Game of Thrones," the White Walkers already made their presence known and made sure that they are one's to be feared and the not the ones who are after the Iron Throne. "Game of Thrones" season 4 "Oathkeeper" give its fans a glimpse of the White Walkers world beyond The Wall where no people dared to go.
Season 4's episode 4 finale revealed the most in-depth look of the blue-eyed monsters and gives fans a hint at what could be expected for GOT's upcoming episodes. In "Oathkeeper," the White Walker took the baby boy from Craster's Keep and rides across frozen seas and places the baby on an altar of ice as a sacrifice, while another White Walker touches the baby's hand and turns him into a new recruit with ice cold blue eyes.
"In that darkness the White Walkers came for the first time. They swept through cities and kingdoms, riding their dead horses, hunting with their packs of pale spiders big as hounds," based on Old Nan's story.
According to the book of "Song of Ice and Fire," White Walkers are a mythological race based on ancient legends passed from one generation from the time of the First Men and Children of Forest. Taller than humans with long wispy white hair, White Walkers have pale white skin and possess magical powers related to ice and cold.
"Game of Thrones" Wikia reads: "Eight thousand years before Robert's Rebellion, a winter known as the Long Night lasted a generation. In the darkness and cold of the Long Night, the White Walkers descended upon Westeros from the farthest north, the polar regions of the Lands of Always Winter. None knew why they came, but they killed all in their path, reanimating the dead as wights to kill the living at their command. Eventually the peoples of Westeros rallied and in a conflict known as the War for the Dawn, the White Walkers were defeated and driven back into the uttermost north, with the Wall raised to bar their return."
Although they are dead, the walkers beyond The Wall can ride undead horses which is even more scary and could give them an instant advantage. Aside from killing humans, the cold-hearted killers seemed to have a strict system and a leader to follow.
Most people in the Seven Kingdoms believe that the White Walkers are just myths, just like ghosts and goblins but they are in for a treat if these monsters will go out after centuries of hiding. Instead of fighting over the Iron Throne, Kings and wannabe kings have bigger enemies as powerful as dragons.