Description: M'uru 2.0. That's all I can say really, Mimiron's Hard Mode is without a doubt the hardest encounter in Ulduar (aside from 0 Watcher Yogg-Saron). It took a few weeks but we finally got our perfect attempt. We could have easilly gotten a kill last week, but we had to replace a few casuals.
After pressing the big red button to enable hard mode, Mimiron's room will begin to explode and spawn doomfire all around the room. I use the term doomfire because it's very similar to the fire from the Archimonde encounter back in Hyjal Summit. In addition to this, Mimiron gains 30% extra damage and health. Throughout the fight Mimiron will try to put out the fires, in each phase he will use a different method to do so.
In Phase 1 he will perform Flame Suppressant, which wipes out all the fires in the room. In Phase 2 he will drop Frost Bombs, which will put out all fires in a certain radius, but also deal 50,000 frost damage to players. In Phase 3, he will spawn Emergency Fire Bots which patrol around the room and put out fires, but also have a 15 yard silencing aura. Finally, in Phase 4, any Emergency Fire Bots that are still up will continue to put out fires, he will also continue using Frost Bombs.
Overall, an extremely challenging encounter that requires an extreme level of coordination and skill. I could not be more proud of our guild for getting this achievement!
All that's left for us is Yogg-Saron Hard Mode and Algalon The Observer!