User blog comment:AnotherRho/Multiplayer Questions/@comment-4835791-20120621080045

The Asari justicar can place her biotic sphere evolved to warp effect in order to set the enemies to detonate with reave. It's very effective againts any kind of enemy specially against barriers and armors. The obvious drawback is that you have to go melee to place the bubble or find a bottleneck where you know the enemies will stay. Ah the other disadvantage is the noise you hear while the reave effect is working.