The Spell Storm
When a spell effect would cause a spell fire explosion in the old world, it instead creates a spell storm in this world.
A spell storm spreads out in a nova like wave from the point of the spell effect.
Depending on the power level of the source, the spell storm can spread from hundreds of feet to hundreds of miles.
The spell storm can affect anything magical in its path. It can cause an item to discharge partially or completely. It can cause an item to become non magical or a permanent effect to fail. It can also cause magic to become twisted and do something other than it was originally designed.
Standard laputan personell transport can self destruct causing a 100 foot spell storm
Basic spell storm will simply negate spell effects 3rd level or less.
Permanent magic items get caster save or go inert for 1d6 rounds.