When the past catches up

Set after the event of HTTYD2. As Toothless discovers his new power, he finds out that being Alpha is not enough. An unknown trial, the forgotten dragon empire, and a secret tribe of mysterious warriors that all came back from the past. The new chief of Berk Hiccup would find his very beliefs shattered as he sinks into the conflict. Can he protect his own? [HIATUS till July]