Sphere: Undeath, secrets
Domain: Knowledge, Undeath
Vecna is the evil god of undead, necromancy, and secrets. He rules that which is not meant to be known and that which people wish to keep secret. Evil spellcasters and conspirators pay him homage. He commands them to:
Never reveal all you know.
Find the seed of darkness in your heart and nourish it; find it in others and exploit it to your advantage.
Oppose the followers of all other deities so that Vecna alone can rule the world.
Published in Dungeon Master's Guide, page(s) 163.