How did White Walkers get created?

Related questions

1. What is the White Walker symbol?
2. Is Jon Snow brother to the Dragon Queen?
3. What is the symbol the night King left?
4. What does the White Walker spiral symbol mean?
5. Why did ygritte shoot Jon Snow?
6. How did Dany get dragon eggs?
7. Who does Jon Snow fall in love with?
8. Who did Jon Snow kill first?
9. Why did Jon kill qhorin Halfhand?
10. What does ygritte say to Jon Snow?

Tags

1. #created
2. #these
3. #against
4. #walkers
5. #daggers
6. #pressed
7. #years
8. #white
9. #chests
10. #sacred
11. #thousands
12. #forest
13. #tribe
14. #cutting
15. #first
16. #slaughtering
17. #protection
18. #create
19. #dragonglass
20. #trees
21. #children
22. #their