The Last Word

You utter a word of power that can compel one God you can see within range to die instantly. You must be powerful enough to become a God yourself and assume their domain's responsibilities. 

Long ago, the Lich Vecna created this spell and used it to destroy the God of Knowledge, Correllon and take his place. The only way to know or learn this spell is by reading the Book of Vile Darkness. To learn this spell from the book requires a DC 30 Arcana check. A failed attempt immediately results in 15d10 psychic damage.

When you cast this spell, make a DC 25 Constitution saving throw. On a failure, you die instantly instead and cannot be revived by anything short of a Wish spell.