How do spy cards work in Gwent?

Related questions

1. Where do I get Ciri Gwent card?
2. What is Gwent Thronebreaker?
3. Is Gwent coming to Android?
4. Is Gwent available on mobile?
5. Is there a Gwent game?
6. How many cards are in a Gwent deck?
7. What happens if you tie in Gwent?
8. How many Gwent cards are there?
9. Is Gwent free?
10. How do you play Thaler in Gwent?

Tags

1. #skellige
2. #count
3. #battlefield
4. #scoia
5. #towards
6. #placed
7. #their
8. #extra
9. #neutral
10. #gwent
11. #opponent
12. #played
13. #monster
14. #allow
15. #total
16. #cards
17. #factions