The next piece of gear is located to the northeast of Oxenfurt. It's directly east of the Temerian Partisan Camp. The exact location has a Signpost called Est Tayiar, and when you arrive you'll want to look inside the tunnel for a brick wall that can be smashed with Aard. Do this, grabbing the Feline Silver Sword Diagram in the process. You'll need the fancy illusion killing device that Keir Metz gave you back in Velen. When you use it, the cave will open, and a short distance inside is a Golem.