How to get King's Oath - Elder Scrolls: Morrowind
Location: Mournhold, Throne Room
Requirements: Complete the Muckraking Journalist quest in a way that satisfies Tienius Delitian
Video: N/A
King's Oath is given to you as a reward for completing the Muckraking Journalist quest in the Tribunal Expansion Pack. There are a couple of different ways that you can complete this quest but only 2 of the ways will reward you with the King's Oath weapon. Essentially, you need to do a good job for Tienius to give you this weapon - if you do a poor job or fail you'll only get credit for finishing the quest.
During the Muckraking Journalist quest you will need to either bribe or blackmail Trels Varis to stop printing The Common Tongue. In order to bribe him all you'll need is 3000G, to blackmail him you'll need to speak with both of his parents in Mournhold about Trels Varis then you'll be able to blackmail him.