I've been having Reverberation fun on my Tempest Cleric with Adamantine Splint Armour, Adamantine Shield, Gloves of Belligerent Skies, Boots of Stormy Clamour, Holy Lance Helm and Blood of Lathander
You miss me with an attack - you get Reverberation (Shield + Boots) and then take Holy damage for another stack of Reverberation (Helm)
You hit me with an attack - you get Reverberation (Armour + Boots)
I hit you with a spell (and since Call Lightning is an AoE spell, you're getting hit) - you get Reverberation (Gloves)
If you're undead and get close - you get blinded.. which means more Reverberation for you
4 stacks of Reverberation and you're flat on your back (you can resist, but thanks to the -4 penalty on your saving throw good luck with that)... oh and you take Thunder Damage which means (thanks to Gloves of Belligerent Skies) more Reverberation for you.
Just waiting for the Thunderskin Cloak - Dazes anyone who hits me and has Reverberation, oh and that should count as "Applying a condition" for my Boots
Ring of Spiteful Thunder - So I can daze you with Thunder if you have Reverberation, oh and that should count as "Applying a condition" for my Boots