After a major miscalculation by Tom in 225 leaves the fate of the Realms in jeopardy, Jun and the riders rally behind Tom and Thunder to face off against the World Serpent.

Tom’s overconfidence turns to frustration then despair as he struggles to procure the ingredients for Gronckle Iron in hopes of building a trap to stop the World Serpent.

Tom attempts to defeat the World Serpent by emulating Hiccup.

The Dragon riders enlist the aid of Carla and Hazel and their scientific knowledge to help them prepare for a mission to neutralize Jörmungandr so they can return him to his chamber and seal him back inside.

Tom and the riders must rescue Plowhorn from Sledkin when the villain abducts the dragon to help her find the Gods Realm and the Dragonsite jewel.

Tom and the dragon riders foster displaced Hidden Realm dragons in Rakke Town but things get complicated when Mr. Rakke makes a surprise visit.