Zath'ras listens to the exchange between the kobolds noting as much as he can understand about what was transpiring with them. Then once these newcomers who have THE key release everyone and open the chest Zath'ras says, "Zath'ras be appreciating greatly the being released. Zath'ras be wondering what you will be doing next. Zath'ras not be wanting to be caged again. Zath'ras would be liking to go with you." as he goes about gathering his things and checking that it was all still there.