Who is Rathma?
The demons of the Burning Hells have the Greater and Lesser Evils, but those seven dark eminences agreed on almost nothing, and as a result, the Hells have almost never been united to a singular purpose.
However much we may look to Inarius as the reason that Sanctuary exists, without Lilith there would be no Sanctuary and no Nephalem.
Wisdom does not mean infallibility.
It's not a demon, it's not an angel, it's definitely not a Nephalem. What is Trag'Oul, and how did it come into existence?
In his time, he has served as the Archangel of Justice and sat as Wisdom on the Angiris Council.
Sescheron, the fallen.
The barbarians of Sanctuary are called this by those who do not understand them or their ancient culture, which was a casualty of the schemes of Baal and the actions of Tyrael. In destroying the Worldstone, they destroyed Mount Arreat and with it the very vigil that the barbarians maintained for countless eons.
For today's Know Your Lore, we're putting on our tinfoil hat and speculating about the nephalem of Diablo 3.