Disclaimer: As well as the usual disclaimer, I must note that the form of the filk is modeled on "Everybody Wants to Rule the World," by Tears for Fears.

Sauron Always Wants to Rule the World – sung by Gandalf, thinking of Frodo

Welcome to the quest
There's no going back
And when you're asleep
He will find you
Come into your nightly visions
There to speak to your derision
Sauron always wants to rule the world
What is your desire?
What is your remorse?
He plays on your fright
He plays on the source
Of all your consternation
Luring you to hesitation
Sauron always wants to rule the world
There's a land where the air is bitter
Shifting sands and with sharp rocks on the ground
Go there, prove that you are no quitter
So close to doing your deed
Don't let your dreams you mislead
Sauron always wants to rule the world
Can you stand to come so far yet
To evil give in and abet
Sauron always wants to rule the world
Say that you'll never never never consent
Withstand all of his torment
Sauron always wants to rule the world
Remember life's small pleasures
Though they cannot last forever
Sauron always wants to rule the world