Detonate

The spellcaster draws all the magical energy inside of their body and releases it in a devastating arcane explosion around them. This causes 1d8 force damage per the spellcaster's level to a maximum of 15d8 force damage. Creatures in a 30ft sphere centered on the spellcaster must make a Dexterity Saving Throw against the spellcaster's Spell Save DC. On a successful save, the creature takes half damage. On a failed save, creatures take full damage.

This reduces the spellcaster's hit points to 0 and sunders their body to the point of no return. The only way to recover the caster after the use of this spell is to gather the ash that remains of their body and cast True Ressurection on their ashes.