Use a Dragon Launcher to kill 50 swarming mantid.
The mantid numbers have been increasing since you left for the cleft. Let's put these orbs you gathered to use.
Get down on the battlefront and man one of the cannons. Let none through.
You will also receive:
- 196,000 experience
- 11 (or 16 48 if completed at level 90)
- 75 reputation with Shado-Pan