Who are the ISU in Assassin's Creed?

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Tags

1. #divinus
2. #known
3. #those
4. #saipens
5. #classified
6. #human
7. #creed
8. #assassin
9. #before
10. #created
11. #civilization
12. #series
13. #ancient
14. #itself
15. #earth
16. #precursors
17. #humanoid
18. #species
19. #advanced
20. #beings
21. #first
22. #video
23. #pieces