Fall of the Royal Capital

Siege of the Royal Capital was the besieging of the Royal Capital of the Re-Estize Kingdom by the forces of the Sorcerer Kingdom during the war between the two nations.

Background
During their war with the Re-Estize Kingdom, the Sorcerer Kingdom knew the key to a swift victory was capturing the Royal Capital. To this end, they centered their entire invasion plan around surrounding and isolating the city in preparation of besieging it. They thus covertly conquered the Kingdom's eastern and northern regions. By the time the Kingdom figured out what was going on it was already too late, as the Sorcerer Kingdom's forces had begun marching on the capital.

As Sorcerer Kingdom's forces headed towards the capital, the citizens were faced with a choice: flee or stay. In the end, many stayed due to them having nowhere else to go. A while later, the Royal Army drafted all the capital's able-bodied citizens into its ranks and set out to confront the Sorcerer Kingdom's forces before they reached the city. However, they were defeated and the entire Royal Army was wiped out.

After learning of the Royal Army's destruction, a defeatist atmosphere took hold of the capital. With the Kingdom's defeat all but certain, those who still could flee the city while the remaining soldiers and Adventurers prepared to make their final stand here. Normal citizens meanwhile, having learned of the Sorcerer Kingdom massacring conquered territories, barricaded themselves indoors; some even preferred suicide over being killed by the Sorcerer Kingdom.

On the Sorcerer Kingdom's side; upon arriving, they surrounded the Royal Capital and set up a base nearby. Following King Regent Zanac's assassination, Sorcerer King Ainz Ooal Gown made up his mind to massacre all the Kingdom's inhabitants that hadn't already surrendered, including the capital's. However, to keep his human sympathizing subordinates appeased, he at least had Eight Fingers evacuate the city's children.

Battle
The Sorcerer Kingdom split it's forces into three, each with their own objective. Cocytus was the overall commander and led the army in taking the Royal Capital. Cocytus with his power froze the gate to the city and broke in and marched through the streets bringing a wave of freezing air that turned everything to ice.

His march was interrupted when he found Brain Unglaus barring his path raising his katana at him in challenge. Respecting Brain's resolve and warrior spirit, Cocytus strikes his Decapitation Fang into the ground and takes out his God Slaying Emperor Blade before assuming a battle stance against him. Cocytus closes the distance between himself and Brain, who is now within his range, and easily ends the warrior's life with one single slash from his weapon. Although the two attack each other at the same time, Cocytus emerges unscathed from the blow, as Brain's blade was not able to reach him. After swinging the God Slaying Emperor Blade, Cocytus shakes off the blood and fat from the katana and returns it back to his Item Box. With the one-on-one fight over, Cocytus pulls his halberd out from the ground and examines Brain's body. Once he takes Brain's katana weapon and commands his Frost Virgins to freeze the warrior's corpse, Cocytus then resumes his walk to Ro-Lente Castle.

Aura having a mission to raid the Magician's Guild scaled the walls of the city with her acrobatic ability. Once she pinpointed the location of the guild using a map, she had her various magic beasts: Fenn, Iris, Gagarpur, a Basilisk, a Amphisbaena, a Kirin, and a Hound of the Wild Hunt climbed out and followed her to their target.

Aftermath
Once the battle was over, the Sorcerer Kingdom had one of its 6th Floor Guardians, Mare Bello Fiore, use his Druid magic to raze whatever remained of the Royal Capital to the guild. Afterward, Sorcerer King Ainz had Guren melt away what remained of the city. As a result, the capital was completely erased like it never existed, with only Ro-Lente Castle being spared to serve as a warning to other nations to not antagonize the Sorcerer Kingdom.