Merton is a dangerous spell which causes a flash of heat so hot it cannot be contained, exploding from your body before you can even focus it into a fireball form. All targets in a 60 foot radius, including the caster, are subject to the spell, taking 2d6+2 points of fire damage per caster level (max 40d6+40 at CL 20th) with a fortitude save for half. Those slain by this spell are reduced to nothing but ash, burning away even bone. It's a difficult spell to use given it cannot tell friend from foe, but for a caster or a party who possesses immunity to fire, it can be a great boon.