Into the Multiverse

Welcome to the multiverse, where every universe is different in some fundamental way. Sure, in our world, what I'm writing is merely fiction, but in another, this is a true story. A story where two of the many universes clash and both worlds are plunged into a state of chaos and confusion. If the source of this catastrophe can't be found, both worlds will tear each other apart, and cease to exist. So... no pressure?
Percy Jackson is sucked into all this when new monsters begin to appear, monsters that even Chiron has never seen. Their weapons are useless against them, even the gods have no way of defeating some of them. Whatever creatures they are, they certainly aren't of this world. The only hope left comes in the form of Regina, the queen of the multiverse. Percy is sent on another long and lifechanging quest to Great Britain with a few of his friends, to do what, he isn't actually sure. He'd just have to wing it, it's not like the fate of two universes were in the balance or anything...