The Darkness Around Us

The mobs are in a courtyard gathering around some adepts/guardians. You can pull them off the adepts and get credit for killing them even if they aren't at full health. If you're also on the Hidden Power quest, those guardians or adepts are the ones you need to deliver the Mantras to.

While running down the stairs they do not aggro, but if they reach their spot and don't find anybody to fight, they'll aggro you (assuming you're in range).

This is a daily quest for the August Celestial faction so you must first get to Revered with the Golden Lotus to unlock it. This is one of 4 diffrent places that the August Celestials have thier dailies, you can either visit all 4 sites (Temples to the Jade Serpent or White Tiger, Cradle of Chi-Ji, and Niuzao Temple) if you have time to waste or you can go to [npc=64001] (Horde) or [npc=64032] (Alliance) in the Vale of Eternal Blossoms (Shine of Two Moons and Seven Stars respectively) to see exactly where the daily hub will be at.

If you can't see the mobs, try flying out of the area (maybe above the Jade Temple instance) and then flying back in.

I couldn't see any of these sha invaders at first. I flew all around the area looking for them, but saw nothing. It was bright and sunny, and there were lots of calm Pandaren NPCs sitting around. I then flew into the outdoor version of the Jade Temple, saw nothing, came back, and then the scene became darker, and there were a ton of sha creatures right in front of the temple.