When Geralt first talked to him, he accused him of spying, showing that he did not trust Nordlings. He did so again if Geralt asked about camp morale, and added that the Nilfgaardian victory was assured and nothing more. However, this may only have been a warning since he was keen to trade and do blacksmith work.
He's located downstairs from the main building of the garrison, where Peter Saar Gwynleve, the captain of the garrison, had his working space and desk.
He only sell runestones after the prologue is finished and Geralt returns to the area.