One of the items you can get from Maidensbane, the Siorc pirate lady in the Coastlands, is called the Emblem of True Power. It's a key item, and the description in your inventory page is:
Maidensbane also mentions that it looks like it slots into a sword hilt. Now obviously this is referring to the King's Thunderblade, the splash text for which says "Let me show you true power." I have both items. My question is, how the hell do you actually slot them together? I've tried walking around, equipping and unequipping the sword, sleeping, going to camp, talking to every blacksmith NPC, and going back to the arena token dude. No dice.