Thread:Leoleosuper/@comment-11200708-20181123193659

https://leagueoflegends.wikia.com/wiki/Turret?curid=2467&diff=2754716&oldid=2754712

did you check the patch notes? https://na.leagueoflegends.com/en/news/game-updates/patch/patch-823-notes#patch-turrets

TLDR:

BULWARK For 20 seconds after a plate is destroyed, the turret also gains Bulwark, granting an additional 25 armor and magic resist for each nearby enemy champion past the first. Multiple instances of Bulwark stack if multiple plates are destroyed within a 20 second window. 