Yes, Dorje Drakden is the emmissary of Pehar who is a powerful "King Spirit" or Gyalpo in Tibetan. He is originally from a region in the Caucasus near what is now Iran and was bound as a Dharma protector by Padmasambhava. Pehar with his retinue is called Gyalpo Ku Nga which includes Dorje Darkden and has a special relationship with the Tibetan government. I think many people would find the energy of Pehar and his retinue a bit to intense to try and use Pehar or his retinue for an oracle themselves - but that is not to say that no one does. There is certainly no exclusivity contract.
Many other oracles were in the past, from another King spirit whose practice the Dalai Lama has actively discouraged in the eighties - This is pretty well with Geluk order mostly. The so called "red hat" orders and Bon are more inclined to use Mountain spirits and protectors of the paticular region they live in. Often such a connection is passed down in families. very popular oracle spirit is "Gesar of Ling".

In the past virtually every township had its own oracle. In more recent times I have seen amongst the Newar people of Nepal (some of who are Buddhist) female oracles of various godesses. I actually met one outside Kathmandu who was a remarkably attractive and charming lady, a mother of four children (who inall honesty looked half her age). She was very easy to talk to and quite "down to earth" when she was not posessed. This is a fscinating subject that remains intact throughout central Asia from Nepal thru to Siberia.
It is funny how in the west such posessing spirits are seen as (and probably often are)quite evil where as in the east they generally are benign. Of course there are evil entities there too but the adepts there in most cases can "control" or at least disarm them.

Minyak

Gesar of Ling is also one of the world's great mythic heroes. There are a couple of English translations of some of his adventures.

Yes thanks Harley.

According to folklore his spirit lives on as a semi wordly Dharma protector especially in the Nyingma and Kagyu traditions. There are people who specialise in a mirror divination method under the aegis of Gesar.

Minyak

Speaking about Oracles: today we started to set-up the "Chamber of Oracles" at the New Surnateum location.
The room is essentially devoted to rare oracle tools from Africa and Asia only. European/American oracles will be displayed somewhere else.
The photo here is just at peek and the room is far from being finished yet.
(Some of the objects on the photo don't have anything to do with oracles)

For the original poster, here is an ebook by Ron Martin and Larry Baukin that covers the subject in detail. I belive this is what Seadog93 was referring to:

http://mevproshop.com/crossroads-spirit.html

It teaches you how to make your own set of aged bones, the first step of which is inviting some friends over and serving a large bucket of KFC. The interpretation method is cartomancy, and the bones are marked and cast in such a way as to signify playing cards to the reader only. The querent sees only bones cast on a cloth.

Sangoma bones.