The Grand Council was alarmed to discover an uprising of AUU mythical creatures from the Planet Ferus as worlds began to get conquered. A mysterious new leader is leading this revolution and made an alliance with known warmongering kingdoms to get involved in it. In order to make sure this problem is resolved, the Grand Council wants the Heroes Act and the Lodgers to go to Ferus and find answers. However, they find out that the armies have grown too large for even them to handle, yet are rescued by a group of peacekeepers called the Magical Creatures and Beings Unity, who have a hold on every known mythological creature planet in the AUU to keep their races from acting out and risk the prosecution of non-mythical beings. The members consist of heroes from several of the races, including the ones that are causing trouble. The group informs the heroes to stay clear of the problem since they are perfectly capable of quelling it themselves. Though the heroes are able to convince them to help since the leaders wouldn't dare to cross people like them, and they agree to help them find what got them to do so as long as they ask the Grand Council not to prosecute the acting-out kingdoms of King Masmash the long-armed ape-like Argosa, King Eyebeam the Cyclops-like Cyclon, King Brawlbone the Minotaur-like Bagargan, King Ogthor the Ogre-like Thater, Queen Lucent the transparent human-like aquatic Trasabix, King Crawgor the human-top and lobster-bottom Hmogst, and Queen Lomira the two-formed Wattira, since their hostile nature is the fault of having incompetent and power-hungry leaders and nothing else. The heroes also realize that mythical creatures are discriminated in the AUU, and the heores feel that they need to build a bridge between these two worlds since science believes that they are not real and those that do know they exist will not hesitate to avoid or even harm them, and the MCBU was made to not only protect the races, but to try and balance out this prejudice as much as possible, hoping that the AUU will bring themselves to care for their kind. And this invasion they're causing needed to be stopped since it would possibly ruin their chances of that happening. The leaders of the MCBU confirm this and admit that it's why they needed to keep them as far away from the Villains Act as possible, though some (like a certain future villain) were minor setbacks they couldn't get to in time. They also confirm that the one responsible for the revolution is an Equestrian Dragon named Cragmire Lucifer the 700th, who had been able to reach the AUU thanks to his alchemy, and is using his dark abilities to turning the normally-scared warmongering leaders into obeying him to conquer both the AUU and Original UUniverses and cause a great mythic beast revolt for how much his family had suffered in the hooves of Pred Judu Des. While aggravated that they had to deal with another person out for blood against Pred, the Lodgers now have to work with the Heroes Act and Unity to stop Cragmire and halt this revolution. However, Cragmire doesn't realize that Pred and his daughters have actually been able to find him thanks to Hidden Shadow, and make sure his death sparks a revolution against mythological creatures for good. With all this trouble arising, how will our heroes deal with this?
(Okay, so far, the only thing I found different was the discrimination part where I added that mythological creatures caused destruction and death. I switched it with your ideal, and made this as much of matching the plot that you prefer as possible.)