Please see
http://nw-forum.perfectworld.com/showthread.php?365641-The-Quivering-Thumb-Arena-Let-The-Games-Begin!!! for the official notice board for the Thumb.
After several months away from Neverwinter, and having been annoyed with the fact that I left the Thumb with a game-killing bug that prevented the quest from being finished, I have returned to provide the much-needed fix that now allows the quest to be completed...given that you are able to survive the many waves of enemies in the pit, first!
Please enjoy, leave reviews and tips, and provide any feedback on what you'd like to see in future updates!
Good luck!