During their search for the escaped Dagur the Deranged, Hiccup and the Dragon Riders discover a mysterious object—one that holds their destiny.

Thinking he's allergic to his best friend Meatlug, Fishlegs gets hypnotized – and wakes up transformed into an invincible warrior known as Thor Bonecrusher.

As a Rumblehorn dragon wreaks havoc on Dragon's Edge, Hiccup seeks the help of Stoick – who forms an unexpected bond with the rampaging beast.

A familiar face joins ranks with the dragon riders, but it's not an easy alliance, especially when Hiccup uncovers a shocking secret about the new member's true identity.

When Hookfang is drawn to a female Monstrous Nightmare, Snotlout tries to break them up before he loses his best friend forever.

A new enemy named Ryker Grimborn captures Stormfly, sending Hiccup, Toothless and the team off to rescue her before it's too late.

When a new tidal class dragon, the Sea Shocker, is found in Edge Cove, the riders must help it escape a group of hungry Scauldrons and reunite it with its migrating pod.