Congratulations! Lina and Momonga!

'''Congratulations! Lina and Momonga!''' (祝邂逅！リナとモモンガ！) is a collaboration game event in Mass for the Dead with characters from Overlord and Slayers. It was released on June 15, 2020 to July 15, 2020.

Background
Luminance between the thrones and regular summoning experiments using Chaos Stones. This time, three mages and one swordsman emerged from another world. One of them, the self-proclaimed "Magical Genius," seems to be powerfulFearless, lightning, and victory is not for whom.

Incident
At might, in the mountains near a post town, screams can be heard from a bandit hideout. The bandits are under attack by an unknown assailant who is throwing out [Fireball]s upon them. The bandit chief coming before their attacker, demands to know why they are being attacked. Their attacker takes the opportunity for a conversation stating that it's ironic coming from people who rib merchants on the highway, kidnap daughters of nobles, and raid towns to ask why. The bandit chief thinks that the townsfolk hired them. To his shock, their attacker states that this is a hobby for her, and he realizes that she is Lina Inverse, the "Bandit Killer." Lina then proceeds to cast another [Fireball] and eliminates the bandit, though she is disappointed that her infamy doesn't account for her being a "Magical Genius," but takes solace that she did a good deed. Her companions, Amelia Wil Tesla Saillune and Zelgadiss Graywords state that killing bandits and stealing their loot shouldn't qualify as a good deed. Gourry Gabriev complains that Lina made them come here all the way out from the inn they were staying. Lina is annoyed by her companions beration, stating no one asked them to come, however, her ire is redirected when the bandit chief, who survived her spell, makes a comment on her flat chest. Annoyed the mage then begins to cast [Dragon Slave] much to the others horror and obliterates the bandit. Amelia chides her for using such magic, but Lina states that the bandit had it coming and the spell wasn't at full strength to avoid damaging the treasure. Zelgadiss wonders if any of the treasure may contain a Philosopher's Stone. Lina doubts that the bandits would be able to handle such a treasure, and just as she goes on a Crack appear behind her. It the proceeds to suck Lina, Gourry, Amelia, and Zelgadiss.

The group eventually land on a carpeted floor surrounded by undead. They are greeted by a being known as Momonga, the ruler of the Great Tomb of Nazarick. The undead then goes on to explain that the four have been transported to another world Though initially shocked by the situation, the group remember the Crack that sucked them in and Lina mentions that the existence of other worlds is possible due to the Sea of Chaos. Momonga is relieved that the group have it easier in accepting to be in another world. Lina however is wary of Momonga, believing him to be some kind of Demon King. While she never heard of his name before, her experience with Fibrizo causes to act with caution. Before Momonga can explain their situation, Lina attacks him with a [Burst Rondo]. The attack fails as it is blocked by a Death Knight, so Lina casts [Raywing] to fly in the air with her companions and escape the room. Momonga interested that the spell she used was similar to [Fly] and not associated with Tier Magic, decides to allow the undead guards outside the Throne Room handle the visitors.

Outside the group land in the Lemegeton where they encounter a horde of undead monsters standing guard. Lina tells her friends to prepare to fight their way out which Gourry, initially shocked by the suddenly escape, happily prepares to use Gorun Nova and fight.

The party manages to make it to the Amphitheater on the 6th Floor, finding very little resistance by the undead horde. They are greeted by two dark elves, and while their appearance are seemingly innocent, Lina's party suspect that is not the case. Lina attempts to ask the children if they could allow them to pass, but are refused, and the two groups end in conflict. One of the elves immobilizes Zelgadiss, by striking his shadow with an arrow. Lina seeing this is similar to [Shadow Snap] attempts to free her comrade by using [Lighting], but is distracted when she almost ensnared by vines produced by the other elf. Lina sensing that the elves and almost all their attackers have been withholding from harming them, decides to surrender. The elf states that is the best outcome as they were given orders not to harm the group, in fact, their master is hoping they could be clients. Confused the group are interrupted when the Floor Guardians arrive at the area. Momonga order Aura to release Zelgadiss which she complies with. The undead highlights that they wish to not harm them and wants to establish a dialogue, though Lina states that they are not going to get along.

Sometime later, Lina and Momonga quickly bond over their interest in magic, comparing them spells used by her and that of Tier Magic. She also takes an interest in Momonga’s thumb ring. Zelgadiss watching this is aghast of the disappearance of all hostility. He soon sees others in his group like Gourry bonding with a fellow warrior, Cocytus and the justice oriented Amelia forming a friendship with Sebas Tian. Not all is well as Albedo grows jealous of the closeness Lina has with Momonga. Shalltear Bloodfallen doesn’t seem to mind, which causes the Overseer Guardian to a accuse her of sympathizing with Lina as they Have the same flat chest. This invokes anger from both women.

After exchanging information, Lina and his friends were sent to the guest room on the 9th floor as a living base for a while. All the members of the group, save Zelgadiss find the inhabitants to be agreeable, especially Lina. Zelgadiss accurately deduces that the mage is aiming to collect some valuables from Momonga. Lina defends her greed stating that maybe one of Momonga’s items could restore Zelgadiss‘s body. Zelgadiss still thinks they should be on guard, however his concerns are ignored as everyone decides to find food. His words falling to deaf ears, the man decides to join them.

A few days after Lina Inverse's party appeared in the Great Tomb of Nazarick, Momonga contracts them to search for a gold vein. Lina wonders why Momonga would need gold as he appears to have enough financial resources. Her employer states that while the wealth around her may seem infinite, it is not and gold is vital for the maintenance of Nazarick. The Overlord plans to use new sources of gold to be converted into YGGDRASIL coins through the Exchange Box. Lina is curious as Momonga is willing to let her party go outside as the possibility of escape could be possible. Momonga doubts that they could escape his forces, and besides if there escape there is no guarantee that they would survive in the current world. Lina gets the points but requests a reasonable share fo the gold. To guide them on this mission, Momonga states that the protagonist and Sebas Tian will be going with them. After Lina's party leaves Momonga asks Albedo and Demiurge about Lina Inverse and her companions. Both agree that the group to possess unique fighting abilities and are well seasoned travelers. Though they are interested in Lina as she was wise enough to understand the difference in power between her and the denizens of Nazarick, though they suspect that that she might be hiding a countermeasure. The two also believe that this mission was an excuse to allow Momonga to study her abilities, though Momonga has no idea what they are talking about. However, he now worries that maybe they are right and that Lina could possess a World Class ability.

At the village of Green Claw, Lina's party, alongside the protagonist, Sebas, Soi, Surako, and Mare Bello Fiore are present. The group are there to investigate a claim by Zaryusu Shasha that gold was discovered. The traveler takes them to the bank of where hunters from his tribe discovered the find. Originally just gold dust was found but there have also been a few nuggets of the precious metal. The lizardmen know the value of money in the outside world, however, due to different priorities the substance was left untouched. However, with a potential gold source nearby the traveler worries about encroaching outside influence may be attracted to it. He is grateful for Nazarick's interest as he came to see them as valuable allies that could resolve this issue. As for the source of the gold, Lina deduces that the gold dust is a result of water being heated by lava when it touched the Great Lake. The lava must have contained traces of gold, and when it was cool, eroded and was deposited into the water. Its highly likely the gold is from the Azerlisia Mountains where lave flows freely in a cavern. Having a destination, Zaryusu offers to escort the team to a safe path to the mountains.

At the foot of the mountains, the group separated from Zaryusu, and began climbing, following the river that fed into the lake. However, even after reaching the peak, they were constantly attacked by monsters like perytons and vultures. Lina figures that this mission of their's doubles not only as a prospecting one but also to reconnaissance the mountains for Momonga. While those like Amelia and Sebas Tian enjoy their skirmishes with their foes, Gourry notices that Zelgadiss is moody. The team camps in a cave created from Mare's magic. After their meal Zelgadiss explains his history of how he was originally human and is seeking a way to restore himself. The NPCs admit such a goal to be difficult, though suggest that the Supreme One might be able to offer him a way however there will have to be a big price paid. Still it may not be possible, causing Zelgadiss to not expect much. A few hours later, Lina is keeping watch over the camp and is joined by Gourry. She tells her companion that she has already been considering asking Momonga if he could return Zelgadiss back into a human, though is unsure if the risk is worth it and whether if it's possible for them to return home. No matter what though Gourry promises to follow whatever path she chooses. They are interrupted by the mumbling of Amelia in her sleep. Lina then decides to a let Gourry keep watch, however fails to notice that Zelgadiss heard their discussion.

The next day at dawn the group descend into a deep cave in the mountains where it reached a place where lava burned bright red. Suspecting that there is an active volcano nearby, Lina believes that they are close to where the gold vein is located. They prepare to go investigate some nearby caves but are also on the watch for any threats.

In one of the caves, Sebas breaks a wall containing a vein of gold. Everyone is excited by the development. Zelgadiss finds it strange as the cave was recently created by something. Given the short amount of time, even for lava flowing within it, the residue gold wouldn't have flown into the lack in such abrupt quantities, reasoning some kind of creature must have burrowed and dug a tunnel. As for what they get their answer when Sebas orders everyone to be on guard. A massive flame is shot through the darkness, and nearly enveloped Gourry, but Mare's [Magic Shield] saves him. Lina putting together the fire attacks and obsession with gold, confirms that the monster they are dealing with is a dragon. Amelia thinks that they should retreat now that they discovered the cause of the incident, but Lina stands her ground unwilling to abandon the gold vein and the mission.

The party then begins fighting the dragon in the tunnel, though are barely holding on due to the confined space and hard scale of the beast. The Nazarick agents pressed against the dragon's attack, urge Lina to use any trump card she has left. Lina is hesitant to unleash her [Dragon Slave] as it could cave the entire ceiling above them. But between life and death, Lina relents and uses her spell, completely obliterating the monster, just as the cave is about to collapse the walls are then reinforced by Mare's magic. Lina suspects that the agents from Nazarick played this out to force her to use her ultimate attack. After Mare covers the gold vein as a safety measure for possible claim jumpers, the party then head back to the dungeon. The scene is watched by Momonga in the tomb, who was impressed by the magical feat.

Aftermath
Back in Nazarick, Momonga praises the group on their success on locating the gold vein in the mountains. The deposited precious ore is reported to be considerable which will benefit Nazarick. Lina is promised a share for her party's cooperation. While she accepts the reward, she also has a request for the Overlord. Momonga having heard from his subordinates reports knows that Zelgadis wishes to change from his chimeraic body back into a human. To her and Zelgadis's surprise, Momonga confesses that he does have a method to restore him to normal, albeit a risky one, that could possibly work but will cost him a lot in return. To be compensated for this feat, Momonga offers to do it on the condition that they offer him everything to him. Faced with a possible cure and a high cost, Lina almost answers yes, but is stopped by Zelgadis unwilling to risk it. He states that he has fully come to terms with his situation, as his body has given him not only strength but also friends willing to do anything for him. Instead, for their achievement in finding the gold vein, Zelgadis asks for a way home.

Momonga grants the request and takes the party to the Throne Room as it was always his intent to send them back. Lina receives a bag of gold for their troubles. The method to return them back to their world as it turns out is through the Crack that they came from. Unfortunately it will be difficult as the Chaos Beasts will be flowing from the other side. At the time of the Crack opening Lina's party readies for combat, where Momonga and the other NPCs witness Lina's magic such as [Ragna Blade] which is viewed as a superior spell to [World Break] as it can tear up space.

Lina then demonstrates another impressive [Ferrous Bleed], which summons a flock of birds. Using the portal within the Crack, Lina connects the current world to her world and vanishes with her comrades. Momonga lauds the ingenuity of the spell to transport Lina's party. Timing with the Crack's summoning of Chaos Beast and performing her own reverse summoning spell went off without any problems. Momonga is slightly disappointed in letting a valuable specimen go, though he decides that it was for the best as it would be dangerous to shelter a being with powerful unknown magic. Granted it would indicate he would have no control over Lina should she have stayed.

In another world, the party finds themselves back at the bandit's camp at daybreak. Everyone is glad to have returned, though a few like Amelia are saddened that they left behind their new friends. Lina is believed to be equally heart-wretched at the parting, however it's revealed that she is crying on losing the gold that Momonga compensated them with when they crossed into the Crack. When reminded about the bandit's loot that Lina was about to claim prior to the incident, she vainly searches for it. However the treasure is nowhere to be found and it's indicated that the bandits must have recovered and left the area after Lina and the others vanished. Unwilling to let the treasure go, Lina declares her intent to hunt down the bandits. In an instant she rushes down the road intent on reclaiming her loot no matter how long it took.