Why is Valyrian steel so rare?

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Tags

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2. #making
3. #valyrian
4. #treasured
5. #steel
6. #those
7. #highly
8. #became
9. #considerably
10. #extremely
11. #weaponsmiths
12. #secret
13. #existing
14. #swords
15. #greatest
16. #always
17. #valyria
18. #weapons
19. #reforge
20. #there
21. #remaining