Thief

This achievement is unlocked during normal story progression and is not missable. It is unlocked when you complete the eighth and final chapter. Note that, although this is the final chapter, it does not complete the game. Post-game play is possible and desirable after finishing the main story.

Chapter eight directly follows chapter 7. Unlike other chapters, there is no opportunity to return to the city after completing the preceding chapter. If you start chapter 8 and quit to the city before completing it, you will have to replay chapter 7 in order to get to chapter 8. Nevertheless, once you complete chapter 8, and thereby earn this achievement, an access point for chapter 8 will appear in the city. At that point, it will be possible to replay chapter 8 without first playing through chapter 7.

The walkthrough provides a streamlined route through chapter 8 including detailed instructions for the final boss encounter. Additionally, it includes a video demonstrating a risk-free approach for the final boss encounter.