Pillager's Hideout (Location)
A bandit camp at the south end of the Valley of Kings. You'll pass through here during the Burnt Offerings side quest.
Both the captain and the treasure tend to be at the southern end of the camp.
Come in from the south rockwall for a stealthy approach, otherwise just snipe everyone from on high for a quick clear. Either way, looting the red chest from that southmost tent completes the location.