According to the Journal of Justice, Kassadin is rumored to have followers called "The Preservers of Valoran". They seek to stop the impending invasion by the creatures of the Void. As such, they are at odds with Malzahar's group, "The Cult of the Void," who seek to unleash the Voidborn onto Valoran.
Zaunite officials speculate that Kassadin's daughter was captured by Malzahar for a sacrificial ritual. She is now trapped within the Void.
Kassadin and Malzahar engaged in combat in the mountains outside of the Institute of War and were eventually stopped by League Adjudicators. Karthus was also present at the scene, though for unknown reasons. He stated that he was "protecting the inhibitor," referring to something other than the inhibitors on the Fields of Justice.