Magical Girl and the King of Magic

Magical Girl and the King of Magic (魔法少女と魔導の王) is a collaboration game event in Mass for the Dead with characters from Overlord and Magical Girl Lyrical Nanoha. It will be released on November 15, 2021 to December 15, 2021.

Background
To be swallowed by the sudden appearance of a crack to a different world that they have never seen. The story of a new encounter and farewell begins at the Great Tomb of Nazarick, where the undead kings and demons live. Magical Girl Lyrical Nanoha Detonation collaboration begins.

Incident
One early morning on Earth in Uminari City in Japan, Fate Testarossa and Hayate Yagami land from the sky at a park to investigate an alert on an anomaly. Though the area is devoid of activity and abnormality. Chrono Harlaown communicating the the two girls via remote from base states that there should be some sort of reaction just 150 meters from them and that the phenomenon may just not be visible. Hayate is curious to know what kind of anomaly they are dealing with but Chrono and those with him don't know as it is unidentified, only stating that it is "a minute space-time distortion that resembles a dimensional earthquake". If left alone it may be cause a serious disaster. Until the containment team arrives to quarantine the area, Chrono orders the two to monitor their position. Supporting the two from afar is Nanoha Takamachi but Fate is worried of her friend's participation as the former has not recovered yet. Despite Nanoha stating that she is fine, her colleagues suggest it is still not wise for her to be overexerting herself.

They get an alert from Amy Limietta that the reaction they detected is now moving...straight towards Fate and Hayate. A Crack manifests in front of the two girls, expanding itself pulling them into a vacuum. Fate summons Bardiche and tries to anchor herself to the ground catching Hayte from being sucked in. The Crack does not let up and increases its pressure to absorb them. To Fate's shock the anomaly even begins sucking her magical energy. Nanoha comes from the air intent on rescuing the two, despite the warning of Fate and Hayate. Flying head first towards the Crack, Nanoha attempts to use Raising Heart but the Cracks succeeds in pulling all three girls in before it vanishes. Chrono and Amy on the other end of the line realize their space-time distortion has vanished. Chrono even suspects that the phenomenon was targeting those three and immediately orders Amy to contact headquarters and the Ursula in order to launch an investigation of where the trio may have gone to.

While the disappearance of the three magical girl caused turmoil for the Tokyo branch of the Time-Space Administrative Bureau led by Chrono, elsewhere taking place in the Great Tomb of Nazarick, Momonga and Demiurge are preparing for a regular summoning experiment in the Throne Room. As they work Momonga is also given a report by Demiurge. It seems that the damages by Chaos Beasts are increasing in the Baharuth Empire. Due to a phenomenon, sporadic hordes of Chaos Beasts are arriving from the central part of the continent and migrating into the territory of the Empire. The information comes as a surprise to Momonga who has been focusing all his attention on E-Rantel since it is the center of all his field operations. Demiurge reports that Nazarick has not been able to deal with the hordes and so the damages to various part of the Empire is increasing rapidly. This is odd to Momonga as he heard that during the early days of the Incident caused by the Cracks, the Empire and the Slane Theocracy were quick to deal with the threats and established a system to deal with the monsters. Unfortunately the lapse in the defenses of the Empire is from the losses of the Imperial Army caused by Jaldabaoth. Not only that the Empire lost many warriors putting down that irregular Chaos Beast horde that attacked E-Rantel. The Floor Guardian adds that the Empire sacrificed much to preserve the key point of the Tripartite Agreement but the end result has left them weak. Not only in numbers but the army now is dealing with emotional trauma from the defeat of the Four Imperial Knights by the Demon Emperor.

Given the magnitude of the problem, Demiurge suggest that the protagonist address it to the emperor so earn his favor. While cause of the Empire's military decline was the result of the schemes of the Sorcerer Kingdom, creating a powder keg that is waiting to happen, Momonga decides to leave the issue alone. At present they have not encountered an individual they cannot handle, though they still have many questions on the Chaos Beasts. The emperor is already has an obsession with the protagonist and Momonga has no wish to burden the latter.

The two are then informed by a Death Knight that the preparations for the experiment are ready. Master and subordinate ready for the new summoning using the Chaos Stones with hopes to summoning a new batch of beings to Nazarick to help in its defense. Though noted such rituals also bring about "exceptions" such as beings from other worlds with valuable information. The experiment is initiated and soon enough Fate, Hayate and Nanoha emerge from the Crack. Once the three girls get their bearings, Raising Heart warns them that they should be careful. Nanoha confused by her Intelligent Device's warning soon sees what she was talking about when she notices the undead summons as well as Momonga and Demiurge. The three are initially shocked by their surroundings and the undead. Momonga seeing them to be just children uses [Mana Essence] and note that they have considerable mana power as well as talking weapons. Feeling guilty for dragging such youngsters to his home and to prevent them from panicking and making the situation turn ugly the Overlord approaches them in peace. The three magical girls are shocked at Momonga, being a talking skeleton but listen to the undead who offers to open a dialogue understanding if they are suspicious and refuse. Unexpectedly, Nanoha accepts to talk first to the surprise of her comrades and Momonga. Nanoha points out to her friends that there is no harm in having a conversation. Fate as well as Bardiche seeing that they are unable to re-establish contact with Chrono agree. Momonga is off put by their willingness to trust him, seeing that he underestimated the three being so young as they value the importance of information. Nanoha introduces herself to Momonga and her comrades and provided him with information of how they arrived.

Nanoha and her friends in turn learn from Momonga about the random summoning from different worlds through the Crack. Fate realizes that they may be on an "non-management world". This is bad as if this is an unknown world that the Time-Space Administrative Bureau is not aware of the rescue may take some time. Likewise from what the girls told Momonga, is is equally intrigued by their magic, Intelligent Devices and the Time-Space Administrative Bureau. Despite the prospects of rescue being slim, Nanoha remains optimistic that they can find a way to return to their original world which her friend share. This comes a bit of a surprise to Momonga given the reality of the situation that the three can maintain a positive and constructive attitude. In fact to him it makes the three appear to be emotionally mature far beyond their age. He envies people that are able to compartmentalize their emotions as he feels that he lacks that quality. Though he hopes to overcome that challenge with time.

Now that both groups have shared what they know so, Momonga wishes to learn more about the girls organization and its technology that allows them to cross dimensions. In exchange he is prepared to offer them the protection of Nazarick while they wait for possible retrieval. The offer is accepted by Nanoha and the others who also accept to do some work for Momonga such as fighting against some threats. On that note, Hayate inquires if such tasks be left to her and Fate as Nanoha still needs to recover from her injury that happened sometime ago. While the request is not unreasonable, Momonga suspects that the three wish to keep Nanoha out to hide their strongest card, but since he can't force them he will allow it. Nanoha insists that she is able to fight and allays her friends fear for her condition. Reluctantly the Fate and Hayate consent to Nanoha's determination. Impressed by their bond, Momonga thanks them for their acceptance. Upon hearing from Nanoha that her magic may not properly work, the Overlord directs her to his subordinates with healing magic to attend to her. After that he sends the trio to rest in their temporary quarters.

Later the next day on the 6th Floor, the three visitors assemble for their first job. Nanoha condition has drastically improved thanks to Pestonya Shortcake Wanko's healing magic to the disbelief of her friends. Aura Bella Fiora and Mare Bello Fiore arrive and introduce themselves to the magical girls and their Intelligent Devices. Fate greeting them is initially confused by their genders since Mare is wearing a girl's outfit. But once finding that it is normal for them, the girl assumes it to be just a cultural thing. Aura and Mare having heard of the Administrative Bureau deals in interdimensional traveling, have thoughts about possibly locating their creator Bukubukuchagama. But they turn their focus back on their charges to prepare them for today's task. They are soon joined by CZ2128 Delta who Aura then introduces to the magical girls. The three magical girls and their Intelligent Devices give the Pleiades member a warm welcome but they are met by a silent response which Aura explains that is due to CZ's personality. For the trio's first mission, Aura directs them to eliminate the Chaos Beasts on the floor.

During the culling of the Chaos Beasts, Fate, Nanoha and Hayate attack and destroy the Chaos Beasts from the air using attacks such as Axel Shooter, Photon Lancer, and Claíomh Solais. The synchronicity and magical attacks impress the members of Nazarick making some realize that Momonga was right to be cautious of them. Even CZ breaks her stoic attitude to acknowledge the hard work of the three girls.

Aftermath
TBA