What does the heart locket do in Undertale?

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Tags

1. #route
2. #heart
3. #armor
4. #neutral
5. #human
6. #first
7. #asgore
8. #associated
9. #offensive
10. #referred
11. #found
12. #locket
13. #genocide
14. #dagger
15. #counterpart
16. #during