http://www.wowhead.com/news=257209/summ ... yn-friends
Soon after zoning into the dungeon, an emote happens, eg "You feel heat in the air rising." It is unclear when the timer exactly starts.
You have a STRICT timing to make it to Opera, kill Opera and click the first Soul Fragment. You have 8 minutes from the moment you zone in, to click the first crystal.
From there on each Soul Fragment you click add a bit of time to your timer. But its very very tight.
If you click all the Soul Fragment within the allotted time, after Curator, you run back to Nightbane's room and Medivh is there and he summons Nightbane.
When you speak to Medivh you get the One Night in Karazhan achievement.
Only one Smoldering Ember Wyrm drops for the group: