User blog comment:Merijnfredriks/Mallury - The King of Death/@comment-24013185-20131212204903/@comment-5028301-20131213072425

His ult is just like nasus/renekton. When he activate it he gains bonus armor/magic resist and attack damage for a short duration. Every soul he owns from his passive makes him 5/10 or 20% stronger (based on level).