It's true that you can find small pockets of Yaks in Afghanistan as well as in Nepal, Mongolia and Bhutan [a few other places including Europe and North America apparently]. However the majority of wild Yaks are found in Northern Tibet and Western Qinghai. I don't know a lot about these regions [CURSE MY SUBPAR CANADIAN EDUCATION] so I'm doing a little research on these regions. As such, I will likely tweak this backstory over time as I continue my research.
I'm mixing together a few cultures as to make the Yaks culturally dissimilar to any irl cultures. My biggest influence was that of the Haida, Mongolian, Chinese and Tibetan people. I can understand that the show staff were probably doing the same thing as I was by borrowing from many cultures but the canon Yaks are kinda annoying.
To begin, Prince Rutherford is now known as Ramzen Yaan [Yaan meaning king in their language] by his people and he's the leader of the nomadic creatures named Yaks. The Yaks are sort of a mixture of Highlander Cattle and Yak. They are MASSIVE creatures and they are larger in height and mass compared to Equestrian ponies. The region the Yaks traverse is known as Yakutiyak Corridor which is found far north of any Equestrian settlements. It's below zero all throughout the year with -1 degrees being considered warm for the summer months. The Yaks like earth ponies, have a unique relationship with the earth and plant life. As such, they travel to different settlements depending on the season to provide better weather for the crops they grow such as root vegetables, flower buds and grasses. They worship a goddess who appears as various wild animals with bright green eyes. The leader of their people is chosen after the previous one dies. On their deathbed, the leader will appoint several of his warriors and then they must compete in numerous trials to decide who will lead. If the leader dies before they appoint multiple successors, the people will appoint several warriors in a diplomatic setting for the same trials.
I plan to draw more about the Yaks because I like them! So there is more to come!