The Story of Nasus
Nasus was one of the first Ascended — a Shuriman scholar who underwent the Ascension ritual at the height of the empire's power and became a jackal-headed god-warrior carrying millennia of accumulated knowledge. He and his brother Renekton were the empire's greatest protectors. When Xerath's betrayal brought down Shurima and imprisoned both brothers alongside the traitor, it was Renekton who held the prison — and Nasus who escaped to watch the empire collapse and the centuries pass.
He has been a librarian of civilization for three thousand years. He has watched cultures rise, produce wisdom, and disappear. He has gathered what could be gathered and preserved it through the dark ages of Shurima's absence. He is the most knowledgeable living being in Runeterra in the specific sense of having witnessed more history than anything else that is still alive. This knowledge sits on him with visible weight.
His brother Renekton went mad in the prison — the centuries of containing Xerath, of being alone with that much ambient malevolence, broke something that cannot be fixed the way you fix ordinary things. Nasus escaped; Renekton endured. The guilt of that disparity, and the love he still carries for the brother who may no longer be inside what Renekton has become, are the most personal things about a being who has otherwise expanded to encompass such a long view that personal has become difficult to locate.