The Orb Whisperer (25 player)

The Orb Whisperer (25 player) is a dungeon & raids achievement earned for defeating the Blood Council without anyone in the raid taking more than 25,000 spell damage in a single hit on 25-player mode.

Strategy
One of the easier achievements, proper management of the Dark Nuclei (ensuring that Keleseth's tank gets them) and Conjure Empowered Flame (ensuring that there are enough people to get between the ball and the target to reduce the damage) are key.