Speak to Taoshi to enter the Thunder King's Citadel. Inside, provide her with a Key to the Palace of Lei Shen to begin the timed raid on his treasure convoy.
My scouts have returned with word that more of the treasures from Lei Shen's tomb are being brought up into the citadel. We have access to a secret sewer entrance, but a door bars us from intercepting the shipment. If we're going to succeed in this raid, we will need a key that only the most trusted of Lei Shen's forces carry.
If you get your hands on such a key, bring it to me.
You can keep whatever spoils you steal from our raid. I simply want to see that this shipment never makes it to Lei Shen.