What is Endo used for in Warframe?

Related questions

1. What is tradable Warframe?
2. Can you sell Built prime weapons?
3. Can you trade non prime Warframe parts?
4. Does Warframe switch cross platform?
5. Can ps4 cross play with PC?
6. Does Warframe have voice chat?
7. Does Warframe need PS+?
8. Can you sell completed Warframes?
9. How much does Warframe platinum cost?
10. Will Warframe ever be cross platform?

Tags

1. #rewarded
2. #variety
3. #large
4. #types
5. #appearing
6. #energy
7. #fusion
8. #process
9. #mission
10. #upgrade
11. #effectiveness
12. #enemies
13. #slain
14. #dropped
15. #commonly