What is the purpose of mitigation in threat modeling?

To actually address or lessen each threat you found — so the software resists attack and users stay protected.

Mitigation means to address or lessen a problem.

The goals of mitigation are:

1. Protect users from security threats
2. Design secure software that resists attacks

Key insight: Mitigation is the whole point of threat modeling - without addressing the threats you find, the exercise is pointless.