[GAME PLAY] Vi Blast Shield Dealing True Damage

During a game I was playing shaco. An enemy Vi with Warrior Enchantment Staukers Blade, Merc Treads, Yoummus, Trinity Force Ice-born Gauntlet and Wardens Mail killed me. After looking at the death recap, I realized her Blast Shield did 700 True Damage to me. How is this possible? Photo of Death Recap