Theart was also hired by Riot Games for the voice of Karthus in the songs `` Deathfire Grasp '' and `` Last Whisper '' by the metal band Pentakill .
He was recently hired by Riot Games as the voice of Karthus in the fictional metal band Pentakill . This was for the songs `` Deathfire Grasp '' and `` Last Whisper '' .