Xenilla and King Sombra battle in the castle's archives. The two are of similar size and physical strength, but Xenilla has a slight advantage because he is used to fighting at range and hand-to-hand, while Sombra preferred to destroy his enemies at range with his dark magic. Xenilla bites him and uses the grip to swing him into walls and windows, until Sombra transforms into a living shadow to escape. Sombra laughs and creates a tsunami of Aerenth. Xenilla defends himself by forming a wall of quartz, but is still knocked back.
Princess Cadance races through the halls, clad in the old suit of enchanted armor. She runs into Lockdown and Dusk Shift, who warn her to evacuate as it is not safe. However, she orders them to help the civilians and alert Shining Armor and the rest of the guards while she handles the fighting. When they protest, she replies, "I was a pupil of the greatest alicorn of our time. She gave me my horn, and I know full well how to use it. You can't protect someone with a shield if you are standing behind them, you need put yourself in front of them. And a true leader needs to do just that. I need you to trust me... I'll be fine." She runs to the archives, but finds the two combatants crashed through the floor and are now in the catacombs.
Sombra boasts that he is the highest form of life, a purebred Unicorn, so a mongrel like Xenilla stands no chance. Bored, Xenilla cuts him off mid-sentence with his Corona Ray, forcing him to dodge. Enraged, Sombra fires several Aerenth shards, but Xenilla blocks them with his own crystals without missing a beat. Sombra sneers; he has memorized the layout of the catacombs, including several hidden items, giving him the advantage. He unearths a sinister black scythe and swings it. Xenilla raises a wall of quartz, but the scythe slices right through it like a hot knife through butter and slashes him across the chest. Xenilla is knocked through the air and into a weapons rack. He struggles to his feet, but the dark magic is inhibiting his healing factor. Sombra attempts to decapitate him, but a spear shaft blocks the strike. Xenilla quickly uses the opening to blast Sombra in the chest with his Corona Ray.
Sombra is blown through the air with his chest armor destroyed and his chest burned. He gets up and demands to know who interfered, and is shocked when he sees what appears to be his ancient enemy Princess Amore Diamante standing before him, screaming that it's not possible as he killed her himself. Cadance corrects him, she is Princess Mi Amore Cadenza.
When Sombra sees her wings, he mutters that his suspicions were correct and the child lived after all. Cadance asks what he is talking about, and he attacks, ranting about how he at least respected Amore for being a purebred Unicorn like him, until she defiled herself by choosing a Pegasus as her husband. As Cadance defends herself with her spear, he declares that this time, there is no dog to save her. Cadance has enough of his confusing talk and presses the offensive, but he disarms her, nicks her several times, knocks her helmet away, and cracks her chest armor with a punch. He boasts that he was trained by the dark sorcerer Grogar himself and tries to finish her off, but she picks up her fallen spear with her telekinesis and impales his shoulder, then boasts that she was trained by her aunt, Princess Celestia.
They resume their fight, and eventually, Cadance blinds him with light from her horn and smacks him in the nose with the butt of her spear, bloodying it. Sombra is beside himself with rage and bombards her with a shower of Aerenth. She defends herself with a barrier, but it starts to crack under the strain. Sombra attempts to finish her off with a Manticore-sized hunk of Aerenth, but a recovered Xenilla destroys it with the Corona Ray, then grabs an axe from the weapons rack and throws it at Sombra's head, forcing him to fall back. Cadance is wary around him, but he says he promised Blade Dancer he'd help her, though he expects a pardon when this is all over. She grants it as Sombra resumes his attack.
Back in Ponyville, Rarity tosses and turns, caught in a horrific nightmare. She sees Manehattan, the Crystal Empire, Canterlot, and finally Ponyville as burning ruins, being stomped to the ground by a silhouetted monster. A mature female voice warns that if "he" arrives in Equestria, all that will remain is death and silence. Then she sees Sweetie Belle's dead body in front of the monster, and falls into despair. Just before she wakes up, she comes face to face with her old evil alter ego, Nightmare Rarity. Extremely shaken up, she checks Sweetie Belle's room. After making sure her sleeping little sister is fine, she returns to her own room and cries. Outside her window, the dark shadow known as the Nightmare Forces nods and flies away.
Xenilla and Cadance clash their axe and spear against Sombra's scythe, and begin pushing him back. Suddenly, Sombra unleashes a huge wave of dark energy. The two try to block it, but it passes through them without affecting their physical bodies. Their minds on the other hand...
Xenilla finds himself in a dark void, and in his true form. He looks around and finds Godzilla Junior, also in his true form but with a gaping hole in his chest. Xenilla frantically rushes over and starts ripping out the crystals sticking out of his body, then crushing them and pouring them into the wounds, but nothing happens. He starts to fall into despair when he realizes his little brother is dead.
Xenilla wakes up to find Sombra laughing at him and Cadance, who is trapped in her own nightmare. Realizing what he just experienced was an illusion, Xenilla is consumed by rage. His entire body glows with radiation and his telekinesis starts lashing out at everything in the room. Sombra stops laughing and is taken aback when he sees Xenilla's shadow change into something that doesn't resemble any equine. Xenilla screams Sombra's name and throws him right through the ceiling. With his concentration broken, Cadance wakes up. She fills her mind with thoughts of love, of her adoptive parents, of her teacher Princess Celestia, and of Shining Armor, the stallion she married. Dark magic is best countered by positive emotions, and the last vestiges of her nightmare fade from her mind. She flies through the hole in the ceiling and has an idea.
Xenilla destroys Sombra's scythe with his axe, then tries to take his head, but misses and the weapon gets struck in the floor. He demands to know what Sombra did to him, even as his vision keeps switching between reality and the nightmare every few seconds. Sombra engulfs him in a wave of hellfire, but he ignores the pain and starts punching, kicking, and biting him. Out of nowhere, Sombra impales him with his horn and then blasts him with dark magic while the horn is still inside him, crippling him with pain. Sombra chuckles and says his technique traps you in your own head as you experience your worst fear. He picks up the scythe's shaft and aims the broken end at Xenilla's throat, declaring, "it ends here, the beast dies alone..."
Cadance steps in and declares Xenilla is not alone, then blasts Sombra away. The energy waves sear Sombra's flesh, but strengthen Xenilla and banish the nightmare. Sombra gets up to find Cadance carrying the Crystal Heart. She fills it with her love energy and the Heart amplifies it and releases it outward, knocking him back again and destroying his Aerenth constructs. Xenilla joins her and they alternate Crystal Heart and Corona Ray blasts, inflicting further and further damage. Terrified, Sombra tries to escape, but the two attack simultaneously and the combined blast seemingly vaporizes him, plus the outer wall and part of a mountain in the distance. All that is left of him is his horn, which vanishes, and his helm. Xenilla stomps the fallen helm flat for good measure.
Cadance says they did it, but Xenilla points out that if Sombra came back once, he can do it again and they should be wary. The light of the rising sun restores his energy a little, but his body is in bad shape and he'll have to rest for a while. Cadance points out she deduced Xenilla's plan of getting arrested on purpose to lure Sombra out. He says it worked and he kept his promise. As he walks away, she notices that his nightmare caused him to cry.
Monster X mediates in his chambers on Zenith, but is caught in a nightmare of his own. He wanders through the ruins of a city and is shocked to find the dead body of a vaguely familiar woman lying on his palm. Suddenly, blood starts pouring from the building windows, boiling up from the streets; and flooding out from the alleys. He is soon waist deep in it and it is still rising. He tries to fly away, but even with all his strength, he cannot escape. As it reaches his mouth and he starts choking in it, pain fires from every part of his body. As the blood reaches his eyes, he hears a voice similar to his own but much deeper say, "Terrible things X... We've done terrible things..." He looks up to see three pairs of glowing eyes and three sets of fanged jaws in the darkness. They lunge at him, and even greater pain fires from his back.
He wakes up and reflexively fires beams that wreck part of the room. Gasping for air, he finds he's bleeding from two spots on his back. The armor on those spots is dented outward, as if something burst from his back. He feels his wounds and finds bone fragments inside.
Xenilla limps down to the prison and unlocks Blade Dancer's cell. She's still mad about getting locked in, but when she sees his injuries, she helps support him as he's almost out of energy and ready to pass out. He says he doesn't need a doctor, just time to heal, so she helps walk him to his room. She gets disturbed by the look on his face; he feels no satisfaction from defeating King Sombra as he's still haunted by the nightmare he showed him. He quickly dismisses her before she can see him break down.
The master of Zenith plots in his sphere. He drains the Alicorn Amulet and the two Electro-Orbs of their power and adds it to his own. However, he is angry at the failure of the Gyaos flock. He had not anticipated that Twilight Sparkle and Mothra would be there to defend the Tree of Harmony, and he had not anticipated that Godzilla would have defended Canterlot. If not for their interference, he would have the Tree of Harmony, Princess Celestia, and Princess Luna before him so he could drain them of their power until they became shriveled up husks like he did to the Alicorn Amulet and Electro-Orbs. He bares his fangs as he thinks of Godzilla Junior and Mothra Lea, saying they are meddling fools just like their father and grandmother respectively. In his rage, he triggers a brief earthquake.
He calms down and remarks that he waited 77000 years to escape his prison, so he can afford to weather a few minor setbacks. He expected King Sombra to slay Princess Cadance and secure the Crystal Heart, but he didn't anticipate Xenilla helping to stop him. Still, this works to his advantage. The Equestrians have no way of tracing Sombra's resurrection to him, so while they waste time trying to find answers in the wrong places, he will continue unhindered. He summons Sombra's severed horn and examines it before setting it aside. As long as he has a piece of him, he can bring him back to life whenever he feels like it. He feels Sombra is a useful pawn, and he will bring him back as soon as he sees the right moment. Then he starts considering other native life forms to manipulate.
Although he is still powerful enough to keep his enlisted Kaiju in line, he is still weak from his long imprisonment and must continue to absorb the power of artifacts and living beings until he is ready. Once he is, he will venture out to personally correct the mistake called life. He will not rest until all life is snuffed out from Equestria, Terra, and the rest of the universe, until all is peaceful in the perfection of oblivion. For he is Extinction. He is Bagan.
Deep in the Everfree Forest, the Tree of Harmony glows and a beautiful creature in hues of silver and amethyst emerges. She strolls through the forest and smiles as the animals stare in awe, the flowers bloom, and the leaves unfold. She is thankful that King Caesar was not the only compassionate one of his kind, thankful for Godzilla saving Canterlot from the Gyaos flock. While she has issues with the Kaiju's willingness to kill, she accepts that death is a fact of life. If ten thousand innocents could be saved and allowed to live as they wished by slaying one irredeemable evil, so be it. She is sad that Godzilla is hated and feared by many of the citizens, but remembers that Celestia and Luna were the same way for a while when they first appeared.
She frowns as she remembers sensing that the Gyaos flock was coated with dark magic, the same as the Kaiju who visited Equestria's human counterpart world. Said dark magic makes it difficult to observe and communicate with them. The true enemy pulling the strings is out there, more evil than even Discord or Lord Tirek. However, she had looked into some of the invaders' hearts and minds and what she saw gives her hope. She has seen the true bond of friendship between Monster X, Gigan, and Megalon. When Irys was terrified that Sunset Shimmer would be put in danger, she was so touched that she had to speak to her and assure her Sunset would be all right. Although she can only speak to them briefly, she believes she can nudge them in the right direction.
She cannot stay in the outside world for long, so she returns to the Tree of Harmony and enters the starry void that is her home. She views through various screens scenes from across the worlds. She sees schools, homes, ocean depths, towns, cities, wilds; and everything in between. Life is the most important gift of all, the chance to make choices, forge friendships, and love. She will do her best to guide champions from two worlds to stop the true enemy who wishes to end it. For she is the keeper of peace and life. She is Harmony.
