Since they're babies, the Night King can change them into White Walkers (his army generals) and train them as they grow up. Craster's sons were given to the White Walkers, and inturn the White Walkers protected him from wildlings and left him alone.
Since many of Craster's daughters did grow up in his life time and he did marry them, it is implied that many of his sons must have grown up as well, albeit as the Others, not as humans. One of Craster's wives confirmed this to Sam after mutiny at Craster's keep: The boy's bothers…
They turn them into more White Walkers. Game of Thrones season 2 shockingly revealed that the Wilding Craster gave up his male children — born of incestuous relationships with his own daughters — as sacrifices to the Walkers in exchange for relative peace in the Haunted Forest.
Most white walkers look to be roughly middle aged and built in body type and basically age only in getting wrinkly skin.
Seclusion. For the next 8,000 years, the White Walkers remained in seclusion in the far North, where some fans think they spent that time in some kind of slumber or hibernation. To quote another fantasy epic: “History became legend.
She said some people believe Night's King was a Bolton, a Magnar of Skagos, an Umber, a Flint, a Norrey, or a Woodfoot. However, she identifies Night's King as a Stark of Winterfell and brother to the King of Winter and suggests his name was Brandon.
In Season 8, Bran reveals that the Night King wants to destroy him because he holds all of the history of man.
The White Walkers want life from male babies. Since they're babies, the Night King can change them into White Walkers (his army generals) and train them as they grow up. Craster's sons were given to the White Walkers, and inturn the White Walkers protected him from wildlings and left him alone.
WEll, they are given infants, they don't just abduct them willy-nilly. That's illegal in Westeros. Apparently, that's how they reproduce. By turning infants into 'white crawlers.
There were no female White Walkers ever seen in Game of Thrones but, based on a story from the books, there could have been a Night's Queen. The Night King and his army of the dead may have become Game of Thrones' major villains, but the show cut the only known female White Walker from the books.
What are White Walkers? Long story short, they used to be humans and now they're ice monsters. They don't appear to speak to one another, but they do use some sort of nonverbal communication.
In A Feast for Crows, she is sent South aboard a ship to Oldtown with Samwell, ostensibly with her child; in truth Jon Snow swapped her child with that of Mance Rayder, to spare the innocent child from Melisandre's flames on account of his king's blood.
Unfortunately, the Children of the Forest lost control of the White Walkers, who threatened to destroy every living thing. During the War Before the Dawn, the people of Westeros, alongside the Children of the Forest, rallied to drive the White Walkers back and Bran the Builder constructed the wall to keep them at bay.
In Game of Thrones, Craster's sons were given to the White Walkers, which is just one of the many things that led sworn brothers of the Night's Watch to detest the Wildling Craster, even though he was one of their few allies beyond the wall.
The Night King Turns Craster's Sons Into White Walkers
As for why babies, and not adults, are candidates for transformation into White Walkers, this is likely because infants are easier to mold into whatever the Night King wishes.
why have the White Walkers waited so long to invade Westeros? What have they been waiting for? The White Walkers have been assembling a massive army that is large enough to invade Westeros/Terros. That takes time, and they need to hunt down as many viable candidates for wighthood.
2. White Walkers are allergic to salt. This theory not only covers the idea of the Night King's army swimming across, but also why they don't use their magical winter abilities to freeze the water and walk across. And it's simple, really: White Walkers are allergic to salt.
First many suggested that Daemon Targaryen was the Night King. Then there was a stir around King Viserys being a White Walker. Now that those theories were shut down, a new theory regarding Aemond Targaryen as the Night King has surfaced.
No, the Night King is not a Targaryen.
In the books, however, the story of the Night King is slightly different. The Night King isn't the leader of the White Walkers. Instead, he's a legendary historical figure who supposedly betrayed the Night's Watch to marry a “corpse queen” and then crowned himself a king.
He was created by the Children of the Forest.
In one of Bran's visions, we see a group of the Children creating a White Walker (presumably the Night King) by tying a man to a tree and plunging dragonglass into his chest until he began to transform.
The Starks May Have White Walker Blood
The House Stark-White Walker bloodline theory suggests that Brandon the Breaker, unable to kill the offspring of the Night's King and his Corpse Queen after they were deposed, instead raised the half-human child as his own.
The Children of the Forest created a "weapon" so powerful they could not control, and for some reason the White Walkers turned against them.
Aside from being a symbol of death, the creation of the Night King was a way to add more history to the fictional universe. The series had the opportunity to dive deeper into the mythology of White Walkers by tying in their creation to the Children of the Forest and the First Men.
During the Battle of Winterfell, twelve White Walkers enter Winterfell along with the Night King to kill Bran Stark. All the White Walkers were destroyed after Arya killed the Night King.
"He wants to erase this world and I am its memory," he explains. As the Three-Eyed Raven, Bran has the ability of greensight, which means he can see events in the past, present, and future through visions. Killing Bran would essentially erase all memory of mankind. Samwell Tarly explains it pretty well in the scene.