Cassius was a soldier of the Zarosian church and a former colleague of inquisitor Aurelius during the Second Age.
"The Shadow" spoke to Cassius, telling him that Zaros had left and that his followers were alone. This challenged his faith and eventually broke his spirit. As a now suspect of heresy, Cassius was detained and tortured by the Inquisition and later questioned by his old friend, Aurelius.
Aurelius tried to change his mind and convince him of the virtue of Zaros's designs, but he was unmoved. Aurelius dismissed his ramblings about the Shadow as madness, and executed Cassius.
- ^ Inquisitior's Memoirs (page 4), written by Aurelius, RuneScape. "Once completed I found myself staring at the file of one of our latest detainees, my old partner Cassius. He was changed from the fiery soldier of the church that I once knew. He was broken, partially because of the torture we'd put him through, but mostly in spirit. Before me was a portrait of shattered faith. 'We are alone.' He kept whispering. 'He isn't there.' [...] I asked him how he knew this. His answer chilled me. 'The Shadow tells me so.'"
- ^ Inquisitior's Memoirs (page 4), written by Aurelius, RuneScape. "I tried to change his mind with words from scripture, but they fell on deaf ears. I tried to change his heart by reasoning that the Empire was functioning to perfection, so Zaros's guiding hand must be present, but he was unmoved. His broken spirit could not be beaten back into shape."
- ^ Inquisitior's Memoirs (page 5), written by Aurelius, RuneScape. "I asked Cassius what this Shadow was and he looked at me with a half smile that sent shivers down my spine. 'Don't you hear it whispering?' he said. 'The statues must hear it. They must. Because it is through them that the Shadow speaks.' Nonsense rambling. Madness. A pity, he had been a good man and a good friend. I took no joy in his execution."