The Primordial War

"' Farquaad relayed only one message to him, “Glory to the true, and to hell with the faithless.” Shrek lobbed the king into a waterfall, and at that moment, The Primordial War erupted between the two titans.'"

The Primordial War was the first major conflict between Shrek and Lord Farquaad. It lasted 5 billion years, and trillions of lifeless pawns perished, and the Swamps were left devastated.

Prelude
Shortly beforehand, Farquaad had stolen Shrek's Blade of the Ages. As Shrek called Farquaad, Donkey, and Fiona to the Temple of the Swamps, and realized what Farquaad had done, he confronted him. Only to be met back with hostility, resulting in the declaration of war.