Classic Era Bug:
The quest The Great Masquerade to escort Marshal Windsor to confront Onyxia is bugging out. It is not possible to continue the quest chain for Onyxia attunement as it is currently.
When you arrive in the throne room the interaction stops at Prestor becoming a dragon. No other continuation of the story/rp.
This occurred on Triala-Thunderfury within a party with Zipzo-Fairbanks.