7 Gates of Chaos
This is part of an ancient spell found in a book that Baron Mordo stole. This spell creates a week of chaos that will ultimately destroy the Earth. 1 gate is opened each day, releasing a daemon of immeasurable power. The 1st gate sets everything in motion. Once it is opened, and the daemon within is unleashed, it can never be closed. The daemon of the 2nd gate will destroy humanity. The remaining gates will destroy the remaining life on Earth, the Earth itself, and ultimately the universe.
The spell is a ceremony that requires the death of 13 magic wielders of at least Adept rank. The daemon of the 1st gate slays these victims. The ceremony for this spell must occur in a permanent ceremonial area of great antiquity.
It is unknown whether or not the text containing this spell still exists. Needless to say, no one but a madman would attempt this spell. But certain daemons or other extra-dimensional beings who want to see the Earth dimension vanish might try it, if the spell still exists.