Flokir is the last main NPC you meet. His journey is considered a side journey and therefore not required for game completion. It starts as part of Eila's Journey with an objective in the Whispers area:
After completing that objective, you start Flokir's journey, which has five steps. The first objective is in the Halls of Klifa:
The second objective is in the Loom:
The third and fourth objectives are in the Bronzed Mire:
The fifth and final objective is in the Gnaw:
You must talk to him in Vagrant's rest after completing each objective and when doing so after his final objective, his Journey will be complete and the achievement will unlock.