After immobilizing an enemy champion, increase your Armor and Magic Resists by 35 + 80% of your Bonus Resists for 2.5 seconds. Then explode, dealing 25 - 120 (based on level) [+8% bonus] magic damage to nearby enemies.
20 seconds Cooldown.
Resistance bonus from Aftershock capped at: 80 -150 based on level.
Flat resistances decreased, percent bonus resistances increased. Flat damage decreased early. Damage now scales with bonus health rather than max health. Cooldown decreased.
Aftershock's flat resistances were eliminating a primary weakness of several ranged champions, forcing us to either balance the rune around edge case users (making it weak for its main audiences), or balance those edge case users around Aftershock (whose mains might not even like Aftershock's playstyle). We're reshaping this keystone back toward tanks and fighters, and will keep an eye on how former(?) ranged users fare in preseason.
COOLDOWN :  ⇒ 20 seconds
| RESISTANCES :
||[70 (+50% bonus resists)]
||35 (+80% bonus resists)
| DAMAGE :
||[10-120 (+4% maximum health)]
||25-120 (+8% bonus health)
BUGFIX : Aftershock's resistances no longer last for slightly longer than intended
Resistances no longer scale with level; now scale with other bonus resistances up to a level-based cap. Damage no longer scales with AD or AP.
Aftershock is taken by a fairly wide variety of champions, especially those with access to hard CC who opt into this rune for a windowed boost of durability. Right now, it looks to be strongest on mages specifically: that extreme durability in combination with high amounts of burst damage mages can provide via Aftershock's AP ratio leaves little room for opponents to play against Aftershock mages. To combat these cases, we're specifically targeting Aftershock's scaling to better hit the same power level for all its users.
BONUS ARMOR : [70-120 based on level] ⇒ 70 (+0.5 bonus armor, max 80-150 based on level)
BONUS MAGIC RESISTANCE : [70-120 based on leve] ⇒ 70 (+0.5 bonus magic resistance, max 80-150 based on level)
| DAMAGE :
||[10-120 based on level (+0.03 maximum health)(+0.15 bonus attack damage)(+0.1 AP)]
10-120 based on level (+0.04 maximum health)
Bugfixing Aftershock's resist duration to do what the tooltip says.
RESIST DURATION :  ⇒ 2.5 seconds
When Aftershock activates, you can't kill its user. Then it explodes, and they damage you. In theory, you should now fight them in their window of weakness, but that window isn't meaningfully long (less than a minion wave!).
COOLDOWN :  ⇒ 35 seconds
Base damage decreased. Damage health scaling decreased but now scales with bonus attack damage and ability power. Flat resistances increased but no longer amplifies resistances by a percentage.
Aftershock's base damage is a bit too high, and it's letting champions like Alistar or Leona run wild in early duels against marksmen. Having one mastery be so good for both durability and damage is warping interactions between tanks and squishier champions, so we're shifting the item profile to be less about damage and more about durability. While we're at it, we're shifting the resistances gain from percent to flat so that divers can get in on the fun, too.
HEALTH SCALING DAMAGE : [3.5%] ⇒ 3% maximum health
DAMAGE : [40-140] ⇒ 10-120 (at level 1-18)
DAMAGE AD RATIO 0.15 bonus attack damage
ABILITY POWER RATIO 0.1 ability power
FLAT RESISTANCES :  ⇒ 70-120 (at level 1-18)
PERCENT RESISTANCES AMP No longer increases resistances by 30%
CALL ME QUAKE After immobilizing an enemy champion, increase your Armor and Magic Resist by 20 + 30% for 2.5 seconds, then explode, dealing magic damage to nearby enemies
DAMAGE 40 - 140 (+3.5% of your maximum health)
COOLDOWN 20 seconds