The War of the Glorious Empire was a period in the history of the World, lasting almost two decades, when the Glorious Empire was expanding as it sought to bring all human kindoms and territories of the world under the control of a single ruler, Emperor Solarius, and exterminate all the magical creatures in existence. This period is considered by the people of the Glorious Empire as a golden age for all mankind (at least before the Fourth Overlord joined the battle), while for all the magical creatures and independent human factions in the world this was considered a dark age of repression, war and genocide. The war ended with the Sack of Empire City, the death of emperor Solarius by the hand of the Fourth Overlord and the disband of the Elven Resistance. The last period of the conflict is shown in the game Overlord II.
Shortly after the Third Overlord was trapped in the Infernal Abyss by the dying Forgotten God and the treacherous Jester and the minions were forced to abandon him, his evil empire began crumbling. After the Great Cataclysm destroyed the dark tower and caused the Magical Plague, the scared citizens of the world were united by a man named Solarius. Solarius attempted to unite the scared and scattered human populations under one banner: The Glorious Empire. Solarius named himself Emperor of this growing, he seeked to get rid of the magic creatures and apparently restore order, but the true ideals of Solarius were not to protect the people, but so he could ascend into godhood, and for nearly 20 years they hunted down magic creatures and imprisoned them for the arena, forcing the remaining Magic creatures such as the fairies, elves and unicorns to form the hidden sanctuaries,and one figure united the magic creatures, the beautiful and good hearted Queen Fay.
The still-expanding Empire is first encountered during the Overlad Prologue. They besiege Nordberg Town and demand they hand over any magic users to be "cleansed". In response, the Nordbergians toss out the Overlad, who proceeds to escape with the aid of the minions and a Yeti. During the time the Overlad is being raised to become the Fourth Overlord, the Glorious Empire expands and takes over much of the World. Their ruler is Emperor Solarius, a ruthless and deluded tyrant, who wishes to eradicate all of the world's magic and collect it in the Magic Containment Room in the Imperial Palace.
Many years later when the Overlord was proving his value to be the reigning Overlord, he came across hunters that were authorized by the Glorious Empire to hunt, and attacked the Overlord, altough they were no match for him and destroyed their camp. The Overlord then proceeded, and found a area with cut down trees, and found that the Glorious Empire had found another sanctuary, and Gnarl suggested to go inside to take a magic relic to power the gates of the Netherworld Tower, which was still uncomplete, but when inside they've seen that the soldiers already taken the relic and Borius was there to oversee the operation. After going through the sanctuary, the Overlord found a stone from the abyss, but was inactive due of his unconfirmed Overlord status, and procedeed, after taking the stone and smashing the gnomes, he became the rightful Overlord fully, and the first Overlord plan was to take Nordberg, which was held by the Glorious Empire, but they had fire barriers to prevent the Overlord from entering the city. After rescuing the reds from the sanctuary, he destroyed the barriers, but the city was protected by an army of legionnares,armed with a ballista, and the Overlord took an alternate path and destroyed the legion, but the city had still armed doors, so he scavenged in a mine that the Glorious Empire was digging to reach the Netherworld, and took several explosives and destroyed the armed doors. He then assaulted the city, which was protected by the legion and some citizens that disliked the overlord, but he massacred them, pushed a stone statue over the Governor Borius and officially started a war with the Glorious Empire. After taking care of the Nordberg, the Overlord reached the shipyard to take a ship and reach Everlight, setting on fire several pites, and possibly destroying the nearby settlement.
Both the Overlord, Elves and the Empire had traveled to the Wastelands, a barren land ruined by the Great Cataclysm, and found its sanctuary. Here, he joined the elves and drained Fay, their queen as the Empire destroyed the last sanctuary.
The Overlord finally launched a major attack against the Empire, he proceeded to conquer the Empire Heartlands and conquer Empire City smashing through its anti-magic shield by catapulting the Tower Heart at the walls of the City, where he finds out Solarius has become corrupt and that the Overlord's Darkness is necessary. After finding Solarius and discovering that he is actually Florian Greenheart who has gone mad with power and must be stopped before he can destroy all traces of good in him. After fighting the newly formed Devourer, the Overlord realizes that in order for there to be evil, there must be good, and the only thing that could destroy a great evil is an even greater evil. The Overlord accepts that he is that greater evil and kills the Devourer, the Glorious Empire fell and the Fouth Overlord takes his rightful place as ruler of all the land as Overlord.