Why does Valyrian steel kill White Walkers?

Related questions

1. Why did children of the forest create White Walkers?
2. What do the white walkers want?
3. What is the Dothraki sacred city called?
4. Who are Arya by caste?
5. What does the name Sansa mean?
6. What race are the Dothraki?
7. Who is the leader of the Night Walkers?
8. Why do the white walkers take babies?
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10. Why were the white walkers created?

Tags

1. #dragon
2. #walkers
3. #according
4. #steel
5. #regular
6. #white
7. #legend
8. #either
9. #flammable
10. #which
11. #valyrian
12. #forged
13. #swords
14. #wights
15. #unscathed
16. #through