The Dark Souls 3 NPC, Greirat the Thief, can become a merchant in Firelink Shrine if you free him from his cell in the High Wall of Lothric area (by finding the Cell Key). Our walkthrough of the High Wall of Lothric tells you exactly where to find the Cell Key and Greirat’s cell in the basement. Once you have the Cell Key and unlock the cell, Greirat gives you a Blue Tearstone Ring and asks you to deliver it to Loretta in the Undead Settlement.
Head to our Undead Settlement walkthrough to find the exactly location of Loretta’s bones. Once you have the item, head back to Firelink Shrine and speak with Greirat. He’ll let you keep the ring and you will retain his services as a merchant.
At times Greirat will ask if he can go out into the world to collect more items and increase his inventory. Speak with him and he will ask to leave once you reach the Undead Settlement (return to him again after delivering Loretta’s bones). It’s safe to let him pillage the Undead Settlement area.
Speak with Greirat again when you reach the Irithyll of the Boreal Valley area and he will ask to leave again for more pillaging. While you can let him pillage this area, he will not survive the trip unless one of two tasks have been completed.
If you’ve delivered Siegward’s armor to him after advancing his story line up to at least finding him in the well in the Cathedral of the Deep area, he will be waiting in the Irithyll of the Boreal Valley area and will save Greirat. If Siegward is not there, you can also have Unbreakable Patches save Greirat. If you’ve already gained Unbreakable Patches as a merchant in the Firelink Shrine, you can also speak with him to keep Greirat safe in the Irithyll of the Boreal Valley area. One of these two has to save Greirat or he will not return from the area.
Finally, when you reach Lothric Castle, if you speak to Greirat he will ask to leave once again. Letting him pillage Lothric Castle will result in his death. Nothing can be done to save Greirat if you allow him to venture into the Lothric Castle area.
Find out more information on the NPCs of Dark Souls 3 or other advice and tips in our walkthrough and guide!