The Ultimate Wars (ウルティメイトウォーズ Urutimeito Uōzu) was a conflict that pitted the army of Alien Empera against the Ultra-beings of the Land of Light over 30,000 years ago. Although Empera temporarily managed to take over the planet, the people of the Land of Light fought back and defeated him.
Although the events are unclear, it is known that Empera took control of the Land of Light after leading the most successful attack on the Ultras, something that various Ultraman's foes had trouble doing. However, his reign was short-lived as the beings of light fought back, initiating the battle between light and darkness.
At the end of the war, Alien Empera and Father of Ultra engaged in their infamous duel that decided the fate of the Land of Light. The results came to a draw and both powerful fighters earned mirroring scars on their hips as a reminder of their brutal battle. Empera, weakened by Father of the Ultra's Ultimate Blade, fled into hiding for generations.
After the war, Ultraman King had Father of Ultra establish the Inter Galactic Defense Force to protect and watch the Land of Light as well as the rest of the universe in case a crisis like this ever happens again.
One of the Ultra Warriors that fought in the war, Ultraman Belial, became wary of the possibility of another assault on the Land of Light. However, his envy towards Ken who elevated to the position of the Inter Galactic Defense Force's Top Commander instead of him clouded his judgement which drove Belial to try to take the power of the land's artificial sun, the Plasma Spark. Belial failed to control the Spark power and was driven out of the Land of Light for his deed. His desire to avenge his exile and power soon reached the spirit of Alien Reiblood, who then turned him into a Reionics and send him back to the Land of Light with his own monster army, and in turn Belial became the very threat he originally intended to avoid.
The war had an impact on various species, how many and the influence is unknown but Alien Temperor wanted to follow Empera's example to conquer the Land of Light, which ultimately failed.
Years later, Empera would make his full return to Earth where he would cause most of the events in Ultraman Mebius. However, he was defeated and ultimately destroyed by Ultraman Mebius Phoenix Brave, making Mebius the first and only Ultra to ever accomplish such a feat.