Nazarick Revitalization Plan -Holy War- (ナザリック再生計画-聖戦-) is a game event in Mass for the Dead that was released on February 28, 2020 to March 16, 2020. The event was re-released on November 30, 2020 to December 15, 2020.
Days after the collapse of the Great Tomb of Nazarick------the restoration plan seems to be on track. However, Momonga foresaw that an unprecedented crisis awaits ahead of the plan. What is Momonga's decision to avoid the crisis------ 
Momonga while resting in his bedchambers is deliberating on the various events that have occurred since the Great Tomb of Nazarick's transition into the New World. From the Non-Playable Characters gaining awareness, to the near collapse of the dungeon from the mysterious Crack in the Throne Room, etc. The Overlord cannot help but be worried as many NPCs have died and the rest have lost majority of their levels after being resurrected to this world. Nazarick's restoration is on track and their situation is improving slowly, however, the information gleaned from Sebas Tian, Solution Epsilon, Narberal Gamma, Slimeko, and the protagonist are troubling and it's only a matter of time before Nazarick falls.
At a meeting in the Round Table Room, Albedo gathers the protagonist, Slimeko and the Floor Guardians for a meeting called by their master. The Floor Guardians wonder at what the purpose of this meeting is for, a few believe that they will be rewarded. However their thoughts are interrupted when Albedo brings them to order when Momonga enters the chamber. At that moment Momonga reveals critical facts on the future of Nazarick. Despite their hard efforts at rebuilding the dungeon, Momonga states that Nazarick will be likely threatened again in the future. Using a report from Demiurge as reference his research shows that the Chaos Beasts take priority on attacking strong opponents, possessing a sense to detect worthy adversaries. Since Nazarick is a place where a great number of powerful beings occupy it, Nazarick will mostly likely be destroyed from an onslaught of monsters. Worse the human nations are also on the decline and are maybe a sign that the dungeon may face the same fate. In addition there are other threats to consider like beings from YGGDRASIL like the Eight Greed Kings that may still exist. In short if they do not come up with necessary countermeasure Nazarick will fall.
The Floor Guardians are horrified of that reality and argue that something must be done. Momonga agrees as declares that an investigation must be started to determine why Nazarick fell in the first place and how to prevent such a calamity from happening again. Demiurge listening to his master recommends they do a survey on a location he recently discovered: the Roble Holy Kingdom that lies beyond the west of the Abelion Hills which Nazarick's forces have occupied. The nation is said to have lost contact with the other nations after being invaded by hordes of Chaos Beasts. Given the lack of human refugees, its assumed by the other nations to have fallen. It is remote enough to openly conduct a survey and possibly reveal clues on how to prevent a similar fate from happening to Nazarick. Momonga agrees and announces that an investigation team will be formed explore the region. Aura Bella Fiora and Shalltear Bloodfallen are selected, due to the former's tracking skills and the latter's combat abilities. To plan to negotiate with possible human survivors, the protagonist, Slimeko and Solution will be sent under the adventurer personas. Albedo agrees to the selection, but before she announces the command to send out the investigation team, Momonga states that another will be joining this team: him.
Albedo and Demiurge are stunned and immediately object to this, reminding him of his safety and station to stay in the dungeon. Momonga argues that his safety in Nazarick is no safer than it is outside with Nazarick's defenses damaged. Plus the Floor Guardians strength are in a precarious state; should the investigation team come across a player like himself they will most likely be killed. He urges them he must go on this expedition for them and Nazarick. After hearing this Demiurge concedes to his master's decision and also invites himself to the expedition, though Albedo pleads to be allowed to join the team. She is rejected as someone must lead Nazarick in his absence. Albedo understanding the needs gives her consent on the condition she see him off through the safe route to the Abelion Hills.
The safe route is revealed to be an underground tunnel constructed by Demiurge using various carnivorous hetermorphic beings. The group traverse through the tunnel to avoid detection and to reach the end where magical beasts will guide the investigation party to the Abelion Hills. On the way, Demiurge provides them information of what he learned so far about the area they will be visiting. Aura's hound detects that they are close to the exit so Momonga then casts [Invisibility] and [Perfect Unknowable] at his subordinates insistence while they establish a perimeter and formation as they mount the beasts.
While en-route to the Abelion Hills, the team is faced with little challenge, save for the occasionally flying beast like Giant Beetles. But thanks to the abilities of Shalltear and Aura they manage to reach the Abelion Hills without incident. There they are greeted by the manager of the territory, Evil Lord Wrath. The Evil Lord welcomes his superior Demiurge to the frontier and immediately gives his report of the progress he made so far. Since he conquered the region, the demon has managed to preserve races that are worth incorporating under Nazarick's control. A few working demi-humans like Stone Eaters working in the area notice Slimeko and Aura. Thinking they are food try to intimidate the girls, but are quickly punished by the Evil Lord for their hubris. He later leads the party to more hospital surroundings of a furnished facility. Once Momonga is there he dispels his invisible countermeasures and Demiurge presents him with a handcrafted skeleton throne for his use, much to his master's silent disgust. Once everyone is settled, Wrath, gives his report of the geography of the Holy Kingdom and how it was originally protected by a Great Wall that bordered the Abelion Hills. He orders several subjugated demi-human tribesman monitor the Great Wall, but so far have not reported any humans fleeing the kingdom. Wrath even sent some demi-humans to investigate beyond the wall but have managed to reach the human city on the other side.
Demiurge decides that they will investigate themselves using their party and any demi-human forces they can bring. Momonga also wants to check the situation at the wall via magic and to the shock of all, the Great Wall is filled with Chaos Beasts far as they can see. Even the sky is polluted with their presence along with a Crack. The group understand that even if they go all out the they wouldn't make a dent in the horde. Momonga still is adamant to go the human city. Wrath agrees to take the group to the wall by first light tomorrow.
The next day, the the group are greeted with a sight of various demi-human and heteromorphic races, like Armats and Magelos working side by side. Demiurge states that there are currently breeding experiments in progress to see if cross-breeding is possible between species. They group make their journey to the wall, with Wrath guiding them. They run afoul of a band of armed goblins but they are quickly scattered by the Evil Lord. The group catch a sight of the Great Wall and are amazed not just by the construction but also by the number of Chaos Beasts surrounding it. Seeing the numbers, Aura comments that the wall that was supposed to protect the nation had the opposite and attracted the Chaos Beasts to the area. Momonga dispels the invisibility and orders Demiurge to proceed with the operation. Taking note the Floor Guardians directs Solution, Aura, and Shalltear to be on standby while he gives Wrath the order to engage the flying Chaos Beasts in the air.
Momonga seeing that Wrath is moving according to plan, begins to make preparations for his spell: [Iä Shub-Niggurath]. The spell instantly kills all the gathered Chaos Beasts in the vicinity of the Great Wall and converts their corpses into Dark Young. The expedition watch from their posts in awe at the display. Evil Lord Wrath is ordered to have his demi-human servants to collect the Chaos Stones left by the slain Chaos Beasts and to be careful as the instant death spell only affects ordinary Chaos Beasts and not the special type Chaos Beasts. Additionally it would be grateful if some were taken as specimens for research.
On the other hand Momonga is satisfied his spell worked. Believing that clearing away the Chaos Beasts is temporary, Momonga decides to do a deeper investigation of the Great Wall which Demiurge agrees. Demiurge then leads majority of the group to explore one the guardhouses of Great Wall and ascertain it defenses and purpose. They deduce that the fortress was managed marginally in shifts by militia personnel due to the near impossibility of staffing a full-time military force. Solution unlocks the door to the interior and they locate sleeping quarters for soldiers and a cache of weapons. The weapons discovered are not magically enhanced ones, causing Demiurge to believe only specialized warriors, like Paladins were gifted such weapons. The lack of human corpses found is an oddity but they assume that there must be a reason. Solution finds another door but is unable to open it as it is locked from the inside. Shalltear then uses brute force to break the door open revealing it to be full of Skeleton Warriors.
The party dispatches the undead and believes that they have found some of the missing soldiers that barricaded themselves in their rooms when the Chaos Beasts invaded and eventually perished. Still that only accounts for a small portion of the people at the Great Wall. The protagonist discovers a diary, which based on their rough translation gives an account of what transpired during the day of the invasion. The party celebrate their success in finding a clue but are interrupted by more undead which they turn to deal with. Later Demiurge contacts Momonga about their progress and states that based on the diary there was a large military exercise at the western center of the Great Wall, where Demiurge assumes to be where the Crack is located recommends that they take the opportunity to examine the Crack in the area. Momonga agrees and allows the demon to conduct his study.
Sadly there is no evidence of any human remains or signs of a battle at the location in the area near the Crack. That is until Aura uses her abilities and to her shock the terrain shows signs that an area effect was casted hence the lack of corpses. This is a power that no Chaos Beast they have encountered so far possesses. To add further credibility to her theory a Gravekeeper is found, its very presence indicating that a large number of people have died in the area recently. The party eliminate the undead in the area, allowing Momonga and Demiurge to safely muse their discoveries. Both find it worrisome that there maybe a high rank enemy in the area. Momonga reports to Albedo back in Nazarick, who has made herself at home in his bedchambers soaking in his bed sheets. Albedo recomposing herself on the other end of the [Message] and tells her lord to be careful which he promises. After communication is cut off the Overseer Guardian returns to fooling around with a Momonga Plushie.
The group come across one of the closest cities to the Great Wall, the city of Kalinsha. Like the Great Wall the damage to the city is great and the area is full of Chaos Beasts. In order to properly conduct their research it is agreed that they would need to go into the city. Since Super-Tier Magic is not possible due to the terrain, Evil Lord Wrath and his Stone Eaters will serve as a distraction to draw the Chaos Beasts away from the survey area. Shalltear and Aura's pet wolf then serve as vanguards to clear up the remaining opponents on their way to the western part of the city where its indicated to be the location of how the city fell. The group make their way to the city's walls and find a number of human corpses. According to the protagonist's estimates and Slimeko's body consumption the soldiers at the city were dead at least four to five months ago. A question is raised how the soldiers of the Holy Kingdom managed to last this against the Chaos Beasts. But it assumed by Demiurge due to their history with the warring demi-human tribes forced its population to have some level of combat training. Unlike the nations in the Tripartite Alliance, the Holy Kingdom is isolated and maintains its solidarity. While those can attribute them as strengths the overwhelming Chaos Beasts made their isolationism their doom.
The number of dead bodies continues to grow. Even more peculiar the deceased are dressed in formal robes and there appears to be evidence of some sort of ceremony had taken place. They locate a collapsed building that may contain books or written material they could salvage. To avoid the obstacles, Slimeko uses her slime abilities to seep through the cracks to retrieve a collection of catalogs, books and a map of the city. Going deeper the are faced with the ruined cityscape. Examining the destruction the group wonder if there was a mass riot or magic involve. Some like Momonga surveying the damage are not sure if this was done a by Chaos Beast but maybe a player. Demiurge gets a report from Evil Lord Wrath stating that his forces are struggling with holding off the swarming Chaos Beasts. This is mind the time to investigate the city s cutting short and they need to narrow their search to find anything relevant.
The protagonist remembering how the Chaos Beasts and Cracks seem to appear in the vicinity of large congregations of living beings, like at the Great Wall in the training area, suggests they go to a place where all the city's populace gather. This takes them to the Cathedral, where the find evidence of a mass gathering of the city's population. It's assumed that the people sought the sanctuary of the Cathedral in prayer to receive their god's protection form the amassing Chaos Beasts, though ironically it proved pointless.
A tremor is suddenly felt by the group from the Cathedral indicating something is inside. Using summons to scout the area, Demiurge confirms that there is a powerful Chaos Beast present in the holy place. He urges his team to be vigilant and prepare to fight. While entering the darkness of the Cathedral, Momonga appears in person after dispelling his invisibility. While his subjects insist he remain remain away from the front-line, Momonga agrees but not before buffing the abilities of Aura, Solution and Shalltear with his magic. As they expect they find a monster in the room, a Giant Chaos Beast before a Crack. Momonga handles this himself and uses two [Maximize Reality Slash]es to eliminate it.
With it gone the party explores the room, noting that there are weapons scattered around the area, strangely no bodies turn up. But the weapons and items indicate they may have belonged to the Paladin Order. Solution takes note of a bunch of materials that are clustered in a corner of the room. Seeing that there is nothing else in the room of value, Momonga orders his subjects to collect it for study. Just as Slimeko and Solution approach the pile and comment on its disorganization a warning is cried out by Demiurge to turn to the sky.
A huge purple dragon crashes through the ceiling with Momonga seemingly in its trajectory. After the dusts clears, Momonga is nowhere in sight. Shalltear fears the worst, until she sees that the new enemy has been injured. Momonga reveals he managed to miss being hit and used [DCracking Mine] to land the first blow on the dragon. Aura sends her summoned wolves to attack the Chaos Beast. In the skirmish the dragon easily kills one of the wolves. Shalltear attacks too, but finds the creature's hide is hard against her Spuit Lance. Momonga orders his subordinates to show the power of Nazarick. Momonga casts [Vermilion Nova] on the dragon proving that while it is resistant to physical attacks, magical attacks are effective. Shalltear is ordered to cast [Wall of Stone] around the dragon and Aura to prepare to use her shooting skills to target the beast. Once the barrier around the beast is formed, the dragon breaks through to face a barrage of arrows from Aura. The dragon is injured but continues to fighting surprising the elf on its pain tolerance. The protagonist observing the creature wonders why despite it having wings why is it not utilizing them in the fight. A realization comes to mind that the Chaos Beasts has inherited the not just the physical form of a dragon but also its avarice and lust for treasure. Momoga presses the attack casting [Napalm] and [Thousand Bone Lane] holding the creature still. Aura, Demiurge, and Shalltear use their respective attacks of [Targeting Skill], [Frost of Judecca], and [Purifying Javelin] to hammer the creature until it finally falls.
The group now free of distraction examine the loot of the dragon, there they discover a strange object. Unable to determine what it is Momonga and Demiurge decide to acquire for their research. The group return to Nazarick and once again convene in council with the other Floor Guardians. Since mission was successful Momonga thanks the NPCs for all their hard work. He then turns the meeting over to Demiurge who then highlights the discoveries made. So far what they learned about the Holy Kingdom was that the nation's cities were in a chaotic state due to the Cracks and Chaos Beasts. In addition they have already pieced together what is perhaps a fundamental rule in regards to the Cracks, in that they appear where large populations are concentrated. For the items collected from the Cathedral, he and Pandora's Actor determined most were holy relics used by priests and paladins with angelic symbology. The existence of angels as summons prove that tier magic was from YGGDRASIL. As for the strange item the found, Demiurge is at a loss for what the item is or its worth to a Chaos Beast but promises to keep analyzing it.
However their answers to do provide sufficient explanations as why the western part of the city of Kalinsha was destroyed. It seemed that the traces of damage was not the work of just Chaos Beasts. Momonga proposes perhaps magic like [Black Hole] or a World Item like Depiction of Nature and Society. What is even stranger is why did the Crack at the Cathedral not cause much damage to the overall area unlike the Crack in the training field near the Great Wall. Mare Bello Fiore wonders how they can prepare for such disasters. Demiurge believes that perhaps their understanding of the phenomena is still not complete. Both Momonga and Demiurge believe it shouldn't be too worrisome as they now have a framework to establish countermeasures and possibly rebuild Nazarick.
Back at Kalinsha, a lone girl approaches the city walls and is amazed at the lack of Chaos Beasts in the area. Believing this to be a miracle she declares that this is proof of God's divine protection and presence.