The Griffin Dominion is located North-East of Equestria. It shares borders with Equestria and Gem Fido.
The Griffon Dominion was a powerful nation a thousand years ago.
The griffins of the Dominion lived in a heavily militarized autocracy. They saw all the neighbouring nations as potential targets to be raided or conquered. They were ruled by a High Commander, who acted as a King of sorts, but they had no royalty. Instead, the position a griffin had in the goverment was directly related to their position in the Dominion army. As such, the High Commander is the general of all the armies, his "lords" and "ladies" are other generals, and so on.
There were noble houses, however, founded by great griffins that reached a position high enough during their lives to ensure their offspring would be wealthy and powerful. However, these noble families could disappear as quickly as they rose, with a sucession of weak griffins quickly depleting their family's fortune until there was nothing left. Due to this, all succesful noble families trained their children since a very early age so they would become great warriors and strategists, ensuring that they would also bring wealth and renown to their family.
Due to their aggresive stance against any non-griffin, the other nations saw them as a dangerous entity likely to steal and kill just for the sake of it. This eventually lead Princess Celestia to dismantle their nation when she had a chance.
The Griffin Dominion as a nation no longer exists. A large percentage of Equis' griffins live as slaves to Gem Fido's diamond dogs. The few who still inhabit the Dominion and are free live in small tribes, so in terms of culture and technology they are in the Stone Age. The Dominion is now home to several diamond dog clans that enslave even more griffins, since the griffins lack the military power to drive them off.