The Story of Renekton
Renekton was the Butcher of the Sands — the Ascended warrior who served as Shurima's greatest military instrument, a crocodile-headed god-warrior who crashed through enemy lines with the specific violence of something that does not make tactical distinctions between targets. He was the blade; Nasus was the mind. Together they were the most effective thing Shurima had ever produced. Then Xerath's betrayal trapped them with the traitor in a magical prison.
Nasus escaped. Renekton stayed, because someone had to hold the prison and Nasus was the scholar and Renekton was the warrior and warriors absorb what scholars cannot. He held it for three thousand years, containing Xerath, containing his own awareness in a space with that much malevolent energy, trying to maintain himself against something that was systematically breaking everything that made him who he was. He failed. Not immediately. Eventually.
He is insane now, in the specific way of something that was made to impose order and was then subjected to three millennia of chaos. The rage is constant and untethered — sometimes tactical, often not. He knows who Nasus is. He knows what Nasus did and didn't do. Whether the brother he loved is still accessible in there, alongside the hatred that Xerath's proximity produced, is the question Nasus cannot answer and Renekton cannot currently ask.