The Acolyte Imperiled quest for Legion Artifact upgrade quests chain.
On the “Defend Ritssyn” step the quest is bugged and Ritssyn just disapears due to layering of new Event. He should go to room next to him and start some kind of an event, but nothing happens. I have tried to abandon the quest multiple times, but no luck.
This is blocking whole Quest Hall chain quests advancement and is blocking the progress.