Dresden's Death curse

When a spellcaster is at death's door, they are able to expend all their magical energy and life force to cast one, final spell: their Death Curse.

This spell will always be cast from the highest-level spell slot the caster has available. Casting it will instantly kill the caster, and only a Resurrection spell or a Wish can bring that ***** back.

This spell can have an incredibly wide range of effects, from creating a high-powered fireball to permanently cursing an enemy to enchanting an item. The player should discuss the exact effect desired with the DM, taking into account the power of the caster, who will decide exactly what happens.