Life in a Different World with the King of Immortals

Life in a Different World with the King of Immortals is a collaboration game event in Mass for the Dead with characters from Overlord and Re:Zero. It was released on January 29, 2020 to February 14, 2020.

Background
A summon experiment using the Rift in the Throne Room and the chaos stones. Before Momonga, four people and one from another world were summoned. One of them, a black-haired boy, was found to have a particular constitution--- Natsuki Subaru's new life in a different world begins.

Incident
Natsuki Subaru along with his comrades, Emilia, Rem, Ram, and Puck after visiting Irlam Village make their way back to Roswaal's Mansion. During their journey through the forest a thick fog envelops the area. Subaru and his friends believe it to be nothing soon are grabbed by a mysterious gust of wind, that spirits them away. Soon after they are gone, the fog vanishes and only silence remains in the forest.

In the ruined Throne Room, Demiurge and Momonga are conducting a summoning experiment, using the Rift. Using a Chaos Stone as a catalyst, the Rift glows eerily and erupted in a brilliant flare of violet light, in which four human bodies are spewed from its mouth. Subaru's group get their bearings together only to see the demon and undead in the chamber. Rem gets into a defensive stance and orders Subaru to get behind her. However Momonga states that they do not wish to harm them. He tells them they are in his domain, the Great Tomb of Nazarick, and wishes if they could peacefully exchange information.

Subaru though terrified at the sight of the skeletons and a Death Knight maintains a courageous face, in the presence of the other women, and introduces himself to the ruler of Nazarick. Momonga explains to the group, that they are no longer in the Lugnica, but were summoned to another world via an experiment. Likewise from Subaru tells him that the world they were pulled from was a fantasy world similar to the new world Nazarick is located in. Bottom line from Momonga's hypothesis they are unable to return back to their world, as they do not quite understand the laws of physics regarding the Rifts. Subaru worries about hi [Return by Death] ability, as it make be connected to the world he was originally transported to. He is afraid without it he will definitely die. Subaru heart pounds, and he clenches his chest as he collapses. His friends worry on his sudden fatigue, but Subaru tells them not to worry. Thinking to himself that he felt the penalty of his ability, it confirms that the [Return by Death] was still present as the Witch's hand effect had activated.

Momonga is more concerned about Subaru's health and offers to give the boy a room so he may recuperate. A skeleton and Death Knight present in the room begin to move toward Subaru, despite Momonga never giving them a order to do so, and begin aggressively moaning at the boy. Rem seeing her friend being threatened, immediately puts herself between them and Subaru. She lands a few blows with her chain ball on the Death Knight with negligible effect. The incident is put to an end by Momonga who used [Napalm] on the undead to bring it back under control. The Overlord sincerely apologizes for the unprovoked attacked. Subaru seeing the display of power and Momonga willingness to attack a subordinate finds it concerning, but thanks the undead nonetheless.

After the two undead are confined, Demiurge humbly apologizes for the outburst of the summons under his watch, but Momonga states it was his responsibility. He wonders what caused the undead to be set off in a savage manner, and turns to his guests if they might known. Ram tells them they don't know but perhaps they should asks Natsuki Subaru for answers. Subaru knowing that he cannot reveal his aura attracts demon beasts due to the penalties if he revealed the nature of [Return by Death] to anyone. He lies that it was his scent that attracts magical beasts, which unfortunately was caused by his sick disposition. Momonga admits that the boy's appearance is poor, though the reason is still shaky, he accepts it at face value. Since there are many magical beings within Nazarick, Momonga orders Demiurge to guide the group to a vacant room on the 9th Floor. After the Floor Guardian and Subaru's group leave the Throne Room, Momonga ponders on Subaru's condition that can attract demon beasts.

In a common room, Demiurge allows the members of Emilia's Camp to make themselves comfortable as he departs. Subaru immediately flops to the floor in exhaustion. The girls scold the young man for drawing attention to himself. Turning to the grandeur of the room, they comment on the financial wealth of their host. Rem is more concerned with Momonga's power, comparing his magical ability to equal or exceeding Roswaal L Mathers. Even Puck admits he cannot divine the limits of Momonga's power and recommends not agitating the undead. Subaru is concerned that Momonga planned the attack on the undead to gain their favor. Rem states that the should focus on returning home as Emilia's Royal Election will happen soon. Puck believes though this world is different from their world, it should still be possible to return home using Beatrice's [Door Crossing], given the doors of her library can open to any location unless certain conditions are met. He believes that by studying the Rifts that they may be able to find a clue to return home.

Aftermath
To Be Added...