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

The dragon riders discover a lush island that turns out to be the home of the Deathsong, a massive, never-before-seen dragon that threatens to trap them forever.

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

Fireworm dragons invade Dragon's Edge, while Ruffnut and Tuffnut discover that they have an unexpected connection to the island.

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.

The dragon riders are surprised to discover who is behind recent attacks on nearby ships – and to learn exactly what the ships are.

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.

After an attack on Berk, Astrid trains a crew of backup Dragon Riders to battle back—but no one can guess how soon the next strike will hit.

The Skrill returns with a vendetta against Hiccup and Toothless. Hiccup and the Riders must choose a new course of action to stop the vicious dragon.

When things don't go well while Fishlegs is in charge, he gets another chance to prove he has what it takes to be a leader.

When a mysterious dragon attacks Spitelouts storehouse, Spitelout and Stoick have different ideas on what to do next.

When the Dragon Riders fly to an island on a vacation, a small creature there has a special effect on the dragons.

Snotlout is sent on an undercover mission to Viggo's dragon auction as part of a plan to rescue the dragons and stop Viggo from getting richer.

After getting bad advice from his father, Snotlout tries to seize leadership of the Dragon Riders and starts making reckless decisions on his own.

Viggo gets angry at the dragon riders continually interfering with his business and uses a deep sea dragon, the Submaripper, to control Berk's trade.

During the week of the Midnight Sun where the sun doesn't set for a week, Hiccup must deal with sleep deprivation and a dangerous new dragon.

After months of planning, Hiccup launches an operation to capture the Dragon Eye from Viggo, only to find that someone else has beaten them to it.

The Riders flee to Berk, where Stoick's plan for defeating the Flyers, which will require a painful sacrifice, spurs Hiccup to seek an alternative.

An unlikely ally helps Hiccup uncover Singetail behaviors that can be exploited to conquer the Flyers. An overconfident Krogan makes a strategy error.

Stoick and Hiccup are led on a wild goose chase in search of willow bark for medicine, leaving Berk vulnerable to an enemy attack.

While on night patrol, Stoick is ambushed by the Flyers and gravely injured, leaving Hiccup torn between his duties as a son and as the Riders' leader.

After learning several Flyers followed Heather to Vanaheim, the Riders must stop them from reporting the sacred island's location to their leader.