Boombox

You create a explosion that activates either when the spell ends or you lose you concentration. If it is dispelled it activates instead of losing its magic.  The explosion deals 25d12 damage to everything within 1000 feet of it. After casting this spell any time you cast a spell that involves fire there is a 50 percent chance that the spell backfires and deals 2d12 damage to anyone (including you self) in a 20 foot cube.