1,300 years have passed since Hiccup Haddock the Third, Optimus Prime and Toothless parted ways. The Dragons and Autobots go to the Hidden World, where Dragons have faded into legend now a new Generation of Dragon Riders will be born in the modern world.
So this takes place between M10: DMC and the up coming M10: AWE. Basically we see what happens while the M10 and their allies and enemies are doing in the year long journey to bring Star Butterfly back
This is just a trailer so read it and tell me what you think.