Look at what I found today while doing my dailies in Ihgaluk Crag – a Trove of the Thunder King. In true Cymre Jones fashion, I was eager to see what kind of treasures it held after such a new and unexpected discovery:

Thunder Plunder - 53,82


On occasion, they may also contain a Key to the Palace of Lei Shen which allows entry to the solo scenario.

To  clarify the drop rates on certain items, Bashiok has stated:

You can only obtain one Key to the Palace of Lei Shen (aka treasure room) from any creature on the island, including the Isle of Thunder Rare Elites. Once you’ve already looted one off of a creature, no more will drop from creatures for your character that week. Additional keys can potentially drop from other select sources, but are extremely rare and not something you can try to farm.

I’m not sure if these treasure troves are unique like the Lost and Found artifacts but it appears that you can only loot one per week (per character). I showed Coolidge where the one I looted was and could not see it when he went to loot it later.