Sion has a 40% chance to ignore up to 30 / 40 / 50 damage each time he is hit by a basic attack. The damage reduction is calculated before armor and percentage damage reduction benefits are taken into account.
Active: Sion surrounds himself with a shield which absorbs damage for up to 10 seconds. After 4 seconds, if the shield has not been destroyed, the ability can be cast again to explode and deal magic damage to surrounding enemies. It will explode automatically after the 10 seconds have passed.