Fool's rune

Every once in a while, some fool decides to inscribe a powerful spell upon a surface, hoping that greedy spellcasters will copy it, upon which moment, the spell will activate, hopefully doing great damage to both the caster and their method of spell storing.
What those fools never realize, however, is that in order to power that permanent spell, they must pour their own lifeforce and magic into it.

— Mangma

Consequences

In order to funnel enough magic power into a fool's rune, a caster loses the ability to cast not just that spell, but any spell of similar power, for a number of years (1d10 years per spell level).

Mangma was the first in known dwarven history to make note of these "spell traps". She gave them the name "Fool's rune" and it has stuck through the millennia.