Revenge of Lavan

What should've been a relaxing day at Los Caballos beach turns into the adventure of a lifetime as visitors from another world try to prevent the return of the evil magma tyrant Lavan, who tried to conquer Equestria in the past. Can they succeed, despite the newcomers having no idea who or what Lavan is? AU taking elements from The Elements of Harmony and the Savior of Worlds.