 While promoting See You on the Other Side in Europe , Jonathan Davis was diagnosed with idiopathic thrombocytopenic purpura , a blood platelet disorder that hospitalized him for the weekend and prevented him from performing at the renowned Download Festival . Despite the illness , the band still performed , with guest singers including Corey Taylor of Slipknot and Stone Sour fame , Trivium 's Matt Heafy , <unk> 's Benji Webbe and Avenged Sevenfold 's M. Shadows . This led to Korn canceling the rest of their European bill for 2006 , including the Hellfest Summer Open Air . It was originally unknown to the public what his ailment was , but the singer revealed in a letter to fans that he was " dangerously low on blood platelets and at a high risk of death from a hemorrhage if the problem was not treated " . 
