How do you unlock Mercenaries in risk of rain?

Related questions

1. How many levels are in risk of rain?
2. How do you unlock a mercenary?
3. What is the point of risk of rain 2?
4. Is Spellbreak coming to ps4?
5. Do lunar coins carry over?
6. How do you get the lunar in risk of rain 2?
7. How many players can you have in risk of rain 2?
8. What are lunar coins?
9. Is risk of rain 2 local coop?
10. What does the rusted key do in risk of rain 2?

Tags

1. #there
2. #reaching
3. #themselves
4. #obelisk
5. #sacrifice
6. #through
7. #appear
8. #unlock
9. #mercenary
10. #about
11. #disagreement
12. #players
13. #portal
14. #celestial