Stormsurge

Stats

Values as the League of Legends Wiki's item data lists them, for every mode; the data doesn't state their units.

Effects

• Stormraider (unique): Dealing damage to an enemy champion equal to 25% of their maximum health within 2.5 seconds inflicts them with Squall (30 second cooldown, starts on Squall's application).
• Squall (unique): After 2 seconds of having applied Squall, strike the target with lightning, dealing 125 (+ 10% AP) magic damage to them. If the target dies before being struck, they emit an electric field instantly that shocks all enemy champions in a cr 600 radius, dealing them the same damage.³

Arena changes

• Ability power changed to 90.
• Movement speed changed to 4%.
• Squall base damage changed to 180.
• Squall AP ratio increased to 30% AP.⁴

For an AP assassin, one build is Boots, Shadowflame and Stormsurge, followed by Void Staff; Rabadon's Deathcap may also be needed, with the last item depending on the champion.⁵

• With Quinn, Sorcerer's Shoes, Shadowflame and Stormsurge are a build; choose Rabadon's Deathcap or Void Staff depending on how much AP augments provide.⁶