Diablo & the party use a magic item to go onboard the emperor’s castle, but Alicia is there right off the bat to stop them. Noa gets into a petty verbal fight with Alicia, before Thanatos and Chobi decide to stay behind to deal with her while the rest go on. The rest of the party fight with the emperor’s tentacles. It’s not even the main body, but Alan loses his right arm because he broke formation and charged in mindlessly, Aila (Isla?) takes a near fatal hit, Edelgard dies, Krum nearly dies, Uttata and Daisy are severely injured if not dead, and Diablo even had trouble destroying the tentacles faster than they keep coming. Max has some kind of healing power rivaling Lumachina, and heals Alan and Isla. Even Diablo was confused since he thought Max was a fighter type. If it wasn’t for Noa using her magic to provide an escape route, they would have been wiped.
Krum and Diablo find god dead after escaping from the emperor’s tentacles, impaled by the Spear of Helvetia which can twist the laws of fate itself. A transcendent magic item unbound by predetermined Akasha, brought from another world. Basically, the Demon/God Slayer. Krum explains how they might be able to win against the emperor if she unleashes her full power (similar to the end of vol 3) but her full killing instincts would return too. Now that she’s restored all her memories, she’s a lot stronger now (even stronger than Modilanam, who was already the closest in power to the founding demon lord). Of course, Diablo could also take the spear, but it drains power from all divine and demonic beings. That is, Diablo would have to give up his demon lord act. It’s painful, but Diablo doesn’t take the spear, and says he’ll kill the emperor without it. So, Krum decides to make Diablo into a true demon lord, and gives him all of her power. Except, it comes at the cost of her life. She didn’t mention anything about dying, so it comes as a surprise. Krum fades away, and Diablo is filled with regret and a newfound power.
Diablo, Edelgard and Krum got split up from Noa’s group when they escaped from the tentacles. After Krum dies, it switches to Noa’s perspective. They leave without bothering to find Diablo and decide to make their way through slim passageways where they can’t be completely surrounded like last time. They get closer and closer, but the tentacles become stronger. Daisy ends up dying protecting Noa, and Uttata dies to a poison attack. Alan goes berserk and cuts through to the throne room, though he breaks his bones and damages his internal organs. That said, Max heals him back to normal. They find what looks like a giant tree. A face appears in the tree; it’s the emperor. He asks who they are, and the question shocks them. After all, they had been fighting his tentacles for so long. It turns out, the emperor did not even consider them a threat, so much as someone walking down the road would consider the insects on the ground to be an enemy. He did not even think of it as a fight. Disinterested, the emperor’s face fades away again. Noa is pissed, and uses apocalypse abyss. Due to balance changes when she played, the spell became a lot easier to cast (same for Gravity Abyss). Max who it turns out is a dark knight, who heals by transferring life force from summon crystals to his team, debuffs the tree. The tree splits open, and inside they find what looks like a magimatic soldier. However, it’s different. It’s the Pure White Cross Reverie – a piece of equipment that belonged to god, and what is thought to be the model for the other magimatic soldier mechs. It doesn’t move at all, so Noa casts a gravity abyss at it, and it gets sucked in. However, though the spell succeeded, a rift in space opens up above everyone, and Cross Reverie comes out.
Noa casts her spells against Cross Reverie, but nothing seems to work. Aside from the exterior being exceedingly tough, it has barriers surrounding it. Isla gets knocked down into a hole in the ground and disappears. Alan tries to attack without any particular plan in mind as usual, but gets killed outright in one hit, such that Max can’t even heal him in time. At this point, all hope is lost. Max tells Noa to escape alone, and Noa, having her life truely threatened for the first time, can only meekly agree. Max puts all his life energy into his sword for one final attack, and manages to break through the emperor’s barrier. However, it wasn’t enough. The emperor lauds him, and would have liked to test his compatibility to see if he would be suitable to be a magimatic soldiers, had Max not sacrificed his own life. Noa tries to escape using a magic item, but the emperor’s magic prevents anyone from teleporting inside or outside the room. Noa has basically given up at this point, when Gewalt, who had been missing this whole time, comes in with a trap worm. Apparently Max had asked him to save Noa if worst comes to worst, and Gewalt couldn’t turn down a handsome man. They manage to escape for a short time, but the emperor slices the worm in two. They end up in a room filled with water and another tree underneath. Gewalt gets a tentacle shoved down his throat in order to test compatibility, and Noa is about to be next, when Diablo shows up. Nobody recognizes him, because he’s covered in armor resembling Krum’s when she was in demon lord form. Noa warns Diablo about the emperor’s barrier, and Diablo tries a new spell to break through. However, it turns out to be much stronger than he expected. Gewalt has sensed the danger in the upcoming fight and already ran away, but Noa was still close by. Diablo’s spell ends up taking the bottom out of the castle entirely, and Noa ends up falling together with the debris, water and parts of the tree. Diablo expects her to be able to use flight magic, but she doesn’t, so Diablo has to save her. Noa, despite being high level, has not ever really had to train hard, and does not really have real fighting experience. When she played Cross Reverie, the game had become insanely easy compared to when Diablo played it. Diablo is holding Noa, and he hears a voice in his head. It’s Krum. She’s able to talk to him and (hopefully) able to return to normal after everything is over. She gives him advice and warnings, kind of like Jarvis and Iron Man. Diablo fights with the emperor, but he quickly realizes that the emperor isn’t simply relying on the power he stole from god. The emperor is extremely capable at fighting. After all, he killed god while he was still just a human. He outwits Diablo several times, and Diablo takes many blows that normally would have killed him, and even forces Diablo to use a full heal potion. On top of that, any damage Diablo does to the emperor gets healed. However, Diablo does manage to land a hit that deals damage faster than the emperor can heal. But, the emperor has a trick up his sleeve. Diablo is struck by a powerful beam out of nowhere, one of the emperor’s many “certain hit” moves that cannot be dodged, and all the Magimatic Soldier mechs (without pilots) come together and strike against the emperor. It’s a combination move. Some of the mechs form the legs, some form arms. The emperor basically becomes a super robot named “God Cross.” Even Krum has given up hope, not having realized that the emperor was able to harness god’s power to this extent. Diablo decides he only has one choice, and puts on all his demon rings. This not only includes the magic reflecting ring from the demon lord of the mind, and the ring of madness from Modinalam, but a third ring, which allows Diablo to use a certain move. However, the constraint is that Diablo becomes unable to cast any other spells.
Thanatos and Chobi are fighting Alicia on the castle. Chobi’s still standing, thanks to Thanatos taking a fatal hit. He’s on the ground, covered in blood. Unfortunately, this time, he won’t revive. The secret behind Thanatos’ immortality is a cape which allows the user to respawn 8 times. That is, the user has 9 lives, and Thanatos was on his ninth. Not to mention, every time you die, you lose memories and your experience goes down, meaning you get weaker. Even knowing that he had no more lives, Thanatos blocked the hit for Chobi. Suddenly, however, Alicia feels the tentacles start to betray her. They want to consume her, but Alicia resists. Instead, Goldinos spits her out, before making its way to the emperor. Even though she was fighting Chobi and killed Thanatos, she had no will to fight on her own. She was under the emperor’s slave magic, and it wore off. Chobi understands this, and spares Alicia.
Meanwhile, the emperor, now in full God Cross robot form, takes hold of Goldinos, which takes the form of a giant sword. Diablo prepares his ultimate move, using the ring from the demon lord Iankaroz. Ruination Flame. The God Cross strikes against it with its own special move: Demise of the Gods – Ragnarok. Diablo can barely hold concentration on the spell, as his hands are damaged and his fingers are severed – his rings gone with them. Not that the magic reflection ring was helping, since the emperor was attacking using the power of miracles – not magic. Diablo’s spell was losing against God Cross’s spell, but, at that perfect moment, Isla comes down from above holding the De-God Slayer, the Spear of Helvetia. When Isla fell down the hole earlier in the first fight against the Emperor, Diablo had saved her, and here she was to repay that favour. The God Cross is rendered defenseless against the spear, and Isla strikes it in the chest section, and tells Diablo to deliver the finishing blow. However, Diablo hesitates. He really doesn’t want to kill Isla. After all, he was asked to save her by one of her comrades. While Diabo is hesitating, Rem and Shera come flying in on a summon – A giant bird. Rem is able to soar through the sky by striking against the air using kikou (not sure how this is officially translated – radiance?). Krum is happy to see that she has finally mastered her abilities as a brawler. Shera sends an arrow at the weakened emperor and takes Isla away. The emperor is elated that the Vessel Girl has finally shown herself in front of him. Diablo chants “Ruination Flame” once more, but the emperor leaves his body, almost like a butterfly leaving a chrysalis, and reveals a snake-like form, and flies straight towards Rem. However, Diablo gets there first to block him. He only chanted the spell without actually focusing magic into it, to trick the emperor. Diablo then blasts the emperor full of magic, such as Infinity Detonation. Unlike a game, where it tells you when a fight is over, Diablo has no idea how much it takes to kill the emperor, so he keeps unleashing spells nonstop into him, buying more time for Rem and Shera and Isla to fly away. However, that’s when Diablo is bathed in a miraculous light. Death.
Diablo and Krum find themselves in a white world, together with an old man in his thirties. It’s the emperor. He dragged them here with his last breath, and reveals that he essentially sold his soul in order to obtain the power to defeat God, and is now cursed to roam this world of nothingness for an incomprehensible length of time. Soon, he disappears. This white realm is known as the corridor to other worlds. Diablo realizes he had once been here before, when he was summoned originally, however he has no memories of it. He hopes to escape, but the only way to escape is through holy power. Unfortunately, neither Krum nor Diablo can do anything. They could wait for Shera or Rem to summon him, however they do not even know that he is here. Diablo learns about the world and magic from Krum, and they remain in this realm for what feels like months or perhaps years. That’s when Diablo hear a calling. It’s a summoning from another world, asking for a hero. The summoner’s name is Mariabel. Diablo decides to go, however, at that last second, he grabs Krum and tries to take her with him, even though it’s a very dangerous task and might cause the summon to fail, leaving both of them to fall in the chasm between worlds. However, it succeeds. Diablo is summoned in a new world, where he meets the summoner, an elf resembling Shera, and her knight. Diablo now has to pretend to be a hero, with his familiar, Krum. The knight tests Diablo, and he wins easily. However, he quickly realizes that neither he nor Krum can use magic. The magic system in this world is very different, where it seems to be based off the stars. Diablo decides to stay here and find clues to return to Lyferia, and finds his room in the basement. And that’s when Mariabel reveals that she summoned him because it was written in their holy book, and also that she must offer her body to the hero. The end.