Royal Signet Ring Location - Elder Scrolls: Morrowind
Location: Mournhold, Royal Palace Throne Room
Requirements: Completion of enough Tribunal Story Quests
Video: How to get the Royal Signet Ring
Royal Signet Ring is found in the Tribunal Expansion Pack and is one of the best if not the best ring in the entire game. Due to the high amount of Restore Health and Restore Fatigue that comes on this ring it makes the person wearing it almost invulnerable. The only way for players to obtain this ring is by killin King Hlaalu Helseth in the Throne Room of Mournhold.
In order to make King Helseth appear you'll first need to complete all the Tribunal Story Quests up until Investigate Bamz-Amschend. Once you've finished this quest you'll be able to find King Helseth in the Throne Room at any point in the future. It's recommended you wait until after finishing the entire Tribunal Story if you plan to kill Helseth for his ring since he is involved in some of the quests in this expansion.
Fighting King Helseth will not be easy by any stretch of the imagination. If you attack him before killing all of the guards in his room you'll have to fight him along with every guard - for this reason it's recommended you clear the room first then attack King Helseth.
Unless you have completed the Helseth's Champion Side Quest there is another item that King Helseth will drop too, the Dagger of Symmachus. Typically this weapon is your reward when you complete the Helseth's Champion Side Quest... however if you've never done the side quest then Helseth will have this item in his inventory instead.