HTTYD 3

One year after becoming chieftain, Hiccup, his Night Fury Toothless and their fellow dragon-riders continue to rescue captured dragons in order to bring them to Berk and its bustling dragon and human utopia. Their efforts have resulted in the island becoming overpopulated with dragons. In response, Hiccup desires to find the "Hidden World", a dragon safe haven spoken of by his late father Stoick. Meanwhile, a white female Fury dragon, held captive by warlords, is given to infamous dragon hunter Grimmel the Grisly as bait for him to capture Toothless for the warlords' use as an alpha.

Toothless discovers the white Fury, (a new species which Astrid dubs a "Light Fury") in the woods, and the two become enchanted with each other until the Light Fury, sensing Hiccup's nearby presence, flees. Hiccup and Tuffnut later discover Grimmel's dragon traps in the area. Grimmel visits Hiccup that night demanding he hand over Toothless, while also revealing he hunted all other Night Furies in the world, but Hiccup has prepared an ambush for him; Grimmel escapes, with his Deathgripper dragons burning down Hiccup's house and most of Berk in the process. Hiccup then rallies the citizens and dragons to leave Berk on a quest to find the Hidden World and safety from dragon hunters.

Mid-journey, the Berkians discover an island on which they initially plan simply to rest, but soon begin to settle there, dubbing it “New Berk”. Seeing Toothless' inability to fly solo hindering his growing relationship with the Light Fury, Hiccup rebuilds an automatic tail for him. Upon receiving it, Toothless flies off, meeting the Light Fury on his own and flying with her to an unknown land. Valka, on a scouting patrol, notices Grimmel's approaching army and reports back to Hiccup. Hiccup and the dragon riders head to capture Grimmel, but fall into his trap and barely escape. Ruffnut is captured, but irritates Grimmel until he lets her go.

Hiccup, Astrid and her dragon Stormfly, searching for Toothless, find the Hidden World and see Toothless and the Light Fury leading the dragons there as a happily mated couple. When the two humans are soon discovered, Toothless rescues them and returns them to the Berkians, with Hiccup realizing his people would be intruders and unsafe in the Hidden World. Ruffnut returns, but Grimmel secretly follows her to New Berk. Grimmel appears and captures Toothless and the Light Fury who had followed them to New Berk. Toothless' alpha status allows Grimmel to capture the rest of Berk's dragons by holding the Light Fury hostage.

With Astrid's encouragement, Hiccup sets out with the dragon riders to stop Grimmel and his army. Gliding on wingsuits, they catch Grimmel's army off-guard, igniting a battle, and freeing the dragons. With help from Stormfly, Hiccup frees Toothless, while Grimmel drugs the Light Fury into obeying him. Hiccup and Toothless give chase and defeat Grimmel's Deathgrippers, but Grimmel tranquilizes Toothless midair causing the dragon to fall helplessly. Hiccup, realizing he cannot rescue Toothless alone, frees the Light Fury and implores her to save Toothless. Hiccup is fully prepared to sacrifice himself in order to save Toothless as both he and Grimmel plummet toward the sea; however, the Light Fury returns to save Hiccup, while Grimmel falls to his death.

Back on the island, Toothless and Hiccup fully realize that dragons will never be safe in the human world. Hiccup bids an emotional farewell to Toothless as all the Berkians tearfully set their dragons free to live in the Hidden World, the Light Fury leading the dragons away and Toothless following them. Sometime later, Hiccup and Astrid finally marry and become the chieftains of New Berk.

Years later, Toothless and the Light Fury have mated and given birth to three hybrid dragon fledglings called Night Lights. Hiccup, Astrid, and their two children sail across the sea to visit them at the edge of the Hidden World. After introducing his son and daughter to his old friend, Hiccup and Astrid take their children flying on Toothless and Stormfly, accompanied by the Light Fury and their offspring. Hiccup vows that until humankind is ready to coexist peacefully with dragons, the dragons will stay hidden while the Berkians guard their secret.