The Arnor are a Precursor faction that had formed prior to the rise of the younger space faring races. They were a noble race that sought to preserve and enlighten the younger races. This brought them into conflict with the omnicidal Dread Lords, who aimed to exterminate them and claim the galaxy for themselves. A desperate civil war broke out between them. With their innate ruthlessness, the Dread Lords devastated the Arnor at nearly every battle. After several systematic lossess, the Arnor learnt of a pocket dimension that the Dread Lords had used to their advantage. In a last ditch attempt to stop them, the Arnor created a device that sucked the Dread Lords into their pocket dimension and sealed them in.
Although they had won the war, it was a phyrric victory for the Arnor, who over the many millennia afterward slowly died out. Only one Arnor lives today.