Princess Sunset Shimmer is not happy about Rodan stating he believes Nightmare Mircalla had let them go rather than them escaping at the end of their encounter last time. When this turns to insulting Rodan by stating he has no right to judge her off the stress she's going through because he doesn't understand, Rodan angrily snaps at her, stating she has no idea what she is talking about with him. He speaks about his origin as a Guardian Beast, specifically born alongside the other Guardian Beasts to fight a god after said god decided one day it would eradicate all life on his homeworld of Terra. And when he was sealed away and then reawakened in modern times, not only was the world he was born into gone in the blink of an eye but now he had been awakened early and was thrown right into the thick of another conflict to protect his planet. All while his original destiny is a ticking time bomb and the thought he's one of those supposed to save his world is actually terrifying to him.
Sunset apologizes, but points out the Nightmare Army still has to be stopped. Rodan says he'll do it. Sunset says he hesitated to kill even one of them, so how can he defeat the entire army? He points out his true form is hundreds of feet tall and will be able to literally stomp on the army. Sunset points out that Mircalla is wearing Nightmare Moon's armor and has her powers, so she can't be defeated with brute force alone. Rodan says at least he can get rid of her army, and he can at least hold Mircalla at bay until they can contact Princess Celestia.
Sunset asks how they change him back to his true form. He struggles to remember, annoying her, then recalls that the kaiju have to be zapped with magic. She is about to blast him, but he stops her and says it has to be positive, beneficial magic, not an attack. He backs away as she gathers her thoughts and power. He privately thinks of how Mircalla let them go and suspects she is not as evil as Sunset thinks. While he's willing to destroy the Nightmare Army, he wants to capture Mircalla and let Celestia deal with her. He admires his version of Celestia for helping convince him and his friends to give Xenilla and Destroyah another chance, and feels Mircalla deserves one as well. He's smart enough to know telling Sunset this out loud is a bad idea.
Sunset powers up an energy beam while filling it with positive thoughts like being adopted by Celestia, hatching Spike, and her adventures in Ponyville. However, her thoughts stray to Mircalla. She's consumed with vengeance and wants to kill her herself. These dark thoughts disrupt her magic and her energy changes from red to black and green. As her magic starts expanding out of control, she feels like she's suffocating in hatred and tries to calm down. Rodan realizes something is wrong and carefully approaches her. She manages to dissipate the dark magic, but her muscles lock up afterwards, leaving her paralyzed.
Suddenly, a squad of undead ponies, all armed with copies of the Alicorn Amulet, attack them. The Unicorns all have enhanced magic, the Pegasi all have advanced weather control, speed, and agility, and the Earth Ponies all have enhanced strength and plant control. Their leader orders Sunset's capture and Rodan's death. With Sunset out of commission, Rodan does his best to fight them, but there are too many. He destroys one with his Uranium Ray, but its body explodes and knocks him down. The others dogpile and start beating and blasting him senseless.
Sunset tries to help him, but she still can't move and can't even fire a blast. Her vision is overtaken by images of her mother's murder at Mircalla's hands. Rodan screaming in agony brings her back to her senses. Determined not to let him die for her sake, she finally manages to move and teleports to him, then unleashes a wave of fire, damaging all of the undead's amulets. This causes all of them to explode. In truth, due to Bagan's hatred of the undead, the amulets had been designed to explode after about 12 hours in order to get rid of them after they had served their purpose, but Sunset just triggered their end a bit early.
Sunset teleports herself and Rodan a distance away and tries to wake him up, but he's bleeding heavily. Realizing he's dying, she desperately blasts him with fire. His body absorbs it and he slowly heals. Once he wakes up, she hugs him and cries, begging for his forgiveness. He hugs her back and says it is okay.
Beyond exhausted, the two hide in a hollow tree and sleep. Some time later, Rodan wakes up to find a Royal Changeling attempting to drag Sunset away. He hisses at it to go away. Scared, it lets go and disappears into the foliage. The Changeling is actually the Warden of the Everfree, once called Fluttershy. Sunset suddenly hugs him in her sleep. Surprised but deciding he's too tired to care, he uses her as a pillow and goes back to sleep.
