This method is as designed per the SA expansion, but I have not seen any documentation about any bit of what I'm about to share with you. So first, this works ONLY for gargoyles, the place you need to get to is only reachable by flying.
We start off by going to a building directly south of the Tomb of Kings entrance along the path. Inside to the right is a pair of books on the floor. The information in the "Book Of Circles" is what the 'quiz' will be on.

After you've familiarized yourself with the content, return to the ToK entrance but go off a little to the east along the mountains. Along the edge where the rocks meet the grass, is a pair of blue sparkles. These are the markers for gargoyles letting them know that you can fly through this area.


Once through the sparkles, find your way between the snow tops into the opening where another building is. The flying path bends slightly to the NW upon first flying the path. Once inside the building, speak the mantra 'Unorus' while standing near the sparkling floor object between the 3 book holding pedestals.

After saying the mantra, you are presented with a quest gump, press continue twice to begin the quiz on what you read. The quiz is similar to that which you took when getting the humiliation quest. You'll be presented with a question with 4 possible answers, and 4 questions total. After successfully answering all questions, you will be able to enter the Abyss from either entrance, through the Kings Tomb, or the underworld.
This is only useful if you find your gargoyle is incapable of killing the monsters that the underworld entrance requires (which was my problem with my crafter as a gargoyle).
Additional info:
- The book to the south of the 'Book Of Circles' contains the mantra word
- Throughout Ter Mur, The Underworld and the Abyss, wherever you see the sparkles, your gargoyle may fly a path between them.
- Humans cannot see the sparkles
Enjoy

SS