(Then I’ll choose that.)
The more the human settlers pushed northward into the highlands and mountains of Eastern Equestria, the more obvious it became that they were not alone.
The Mountain range was dominated by a confederacy of dozens of Gryphon clans.
It was headed by its first king, Giorgy I, who was protective, militant and eternally suspicious in equal measure. And he responded to the human intrusion into their realm with blunt violence.
Gryphon skirmishers would effortlessly pick off the explorers from above, ultimately sending every human mission falling back to the coast.
As the Gryphons had spent the last millenia locked into a constant border struggle with emerging changeling hives, they did not view the arrival of man kindly.
And if man wanted to cross their domain, he would have to pay.
Either with copper, or with blood.