Fall of Ro-Lente Castle

Fall of Ro Lente Castle was the besieging on the Royal Palace of the Re-Estize Kingdom by the Sorcerer Kingdom's forces amidst the war between the two nations. It also saw the assassination of King Ramposa III as well as the defection of Princess Renner to the Sorcerer Kingdom.

Background
Following the Sorcerer Kingdom's siege on the Royal Capital of the Re-Estize Kingdom, all that remained unconquered was the Royal Palace, Ro Lente Castle. Inside were the last remaining members of the royal family, King Ramposa III and Princess Renner, protected by their knights, who were preparing to make their last stand. With the Kingdom's defeat all but guaranteed, Princess Renner seemed to be planning to commit double suicide with her father to evade capture.

In actuality, though, Princess Renner had been a Sorcerer Kingdom spy as early as the Demonic Disturbance and was, in fact, plotting to assassinate her father as a display of fealty towards the Sorcerer King. While her full motives remain unknown, two possibilities can be drawn: 1. It was a test given to her by the Sorcerer Kingdom; 2. She became worried about her position after the plan was changed into an all-out invasion.

In preparation for the assassination, Princess Renner made sure to remove all possible obstacles to her "play." Although it is unknown if she anticipated it, Blue Roses fled once the kingdom's defeat became certain while Brain Unglaus went ahead to make his last stand during the siege. As a result, the only person-of-interest remaining was the Princess' bodyguard, Climb. She thus send him on a mission to hide the crown jewels throughout the capital to prevent the enemy from acquiring them. In reality, though, the bodyguard was actually placing the jewels in pre-determined locations to be retrieved later by the Sorcerer Kingdom.

On the Sorcerer Kingdom's side, there seemed to be little-to-no preparation for the castle siege, with their main invasion commander Cocytus making a straight path towards the palace; instead merely waiting for Princess Renner to give the green light.

Battle
The exact events of the battle are unknown. However, by the time Climb returned from his mission the castle had fallen, with all its inhabitants having been killed; except Princess Renner. The Princess also successfully carried out her assassination plot by stabbing her father in the back with the royal sword, Razor Edge, right in front of Sorcerer King Ainz and his retainers, Albedo, Demiurge, and Cocytus. Climb who had returned from an errand witnessed the act. He stood between her and the opposing party ready to face them on his own. Demiurge had already removed him as a threat, casting a mental command to order the bodyguard to kneel before Ainz Ooal Gown. Experiencing this, Climb believed that this was how Ainz was able to kill her own father. The Sorcerer King getting a closer look at Climb, recognized him as the one who was there when he killed Gazef Stronoff. The undead summarily order his subordinate to remove the [Command Mantra] allowing the boy to stand and face him. Climb was offered a duel with the Sorcerer King, with his life and the ownership of Razor Edge on the line. Fueled by anger for what the Sorcerer King made his mistress experience Climb threw Razor Edge right at the undead sovereign who lost his balance avoiding the weapon. CLimb then followed-up with a strike from his fist. The blows were hardly noticed by Ainz, who merely grabbed Climb from his breastplate and held him in the air like a toy and threw him to the ground. The undead told the defeated warrior that the world he existed in was full of inequalities and should accept his limits and die as it is the only true equalizer for all. Climb refused to give into the despair, and looked at Ainz with defiant eyes which impressed Ainz reminding him of Gazef's eyes when he killed him.

It was then did Ainz acknowledge Climb and decided to properly duel him in a test of swordsmanship, conjuring a blade to face Climb and Razor Edge. Before dueling Climb bid Renner to escape and charged at the Sorcerer King. Despite his tries, his blade was parried by Ainz, making no move to attack but rather toy with the warrior. Angered at being looked down upon, Climb focused one strike at Ainz, betting on everything on that blow. His target was the red orb in Ainz's chest believing it to be a weak spot. But the attack was caught dead in its tracks by the Sorcerer King with a single hand. Climb though had been injured by a slash from Ainz's blade forcing him to retreat.

Ainz deeming the duel to be over move forward to end as he was eager to claim the sword and study its potential effect. He then casted [Grasp Heart] on Climb, killing him instantly.

Aftermath
This operation effectively saw the final dissolution of the Re-Estize Kingdom's central government. Though the Kingdom still had territories remaining that were yet to be subjugated, after the battle the Sorcerer Kingdom spread out its forces to take these as well. Sure enough, without the government's aid, these small independent domains would fall with little-to-no resistance.

Such incident was also served as the final screening test for Princes Renner's admission into the hierarchy of the Sorcerer Kingdom, where the Sorcerer King's three closest aides; Albedo, Demiurge, and Cocytus and the Sorcerer King himself personally take an open analysis on Renner and her overall capabilities as a potential asset or potential threat against their Kingdom should she join. With Albedo and Demiurge having successfully obtained a full grasp on the Former Princess's personality, intelligence, motivations, and overall abilities, this successfully convinces them that they could handle her without much difficulty.

This operation even served to act as the building stage for the Third Princess's personal plot to manipulate her faithful and loving dog, Climb. Once he had been revived by Pestonya Shortcake Wanko, she ensure that he not only remain loyal to her but also have him become loyal to the Sorcerer King upon her revealing her defection to the Sorcerer Kingdom and transformation into an Imp.

During the interval between Climb's "mission" to hide the Royal Treasures and his return to the Royal Palace, Renner had already set up the entire stage for his "Duel" against the Sorcerer King by successfully setting it up as if she was compelled by Demiurge's [Command Mantra] to unwillingly kill her own father and set up his "Heroic last stand" against the Sorcerer King to go smoothly.