Kill him in two rotations. Drops calcified fragment, emblem and a 320 artifact :D
Edit 1: Doesn't have to be done in two rotations as long as different people are grabbing the aura. You also get a 320 weapon of some sort to drop as well on hard mode. When we did it no info was available about this. I was trying to help out and get this info out asap.
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What challenge??