Dragon Hunter War

The Dragon Hunter War was the war between the Dragon Hunters, the Dragon Riders, and their respective allies in Dragons: Race to the Edge.

Background
Following Dagur's escape from Outcast Island, Hiccup and his riders then went after him and journeyed to the Ship Graveyard in "Dragons: Mystery of the Dragon Eye". In truth, Trader Johann allowed Dagur to escape as part of a plan to rid the Barbaric Archipelago of dragons as he revealed in "In Plain Sight". There, Hiccup discovered the Dragon Eye aboard the Reaper in "Dragon Eye of the Beholder, Parts 1 and 2". Hiccup briefly lost it, but reclaimed it in "Dragons: Mystery of the Dragon Eye".

Hiccup's riders then established a outpost on Dragon's Edge in order to find Dagur and learn more about dragons there in "Dragons: Mystery of the Dragon Eye".

Dragons: Race to the Edge, Season 2
Astrid is the first to discover the Dragon Hunters in "Night of the Hunters, Part 1". Being led by Ryker Grimborn, they captured Stormfly and headed out to the sea, leaving Astrid floating in the water.

Later, all the riders came in Stormfly's rescue and attack a few ships. However, due to them not knowing the enemy, all but Hiccup, Snotlout and their dragons are captured. While putting the riders in cages, they met Dagur and Heather, who have allied themselves with the Dragon Hunters.

In "Night of the Hunters, Part 2", Ryker showed the captured riders how their dragons are used against their will, to provide the hunters with weapons, Gronckle Iron and clothing material. The riders then tried to escape, but failed.

When Hiccup, Snotlout and their dragons attacked the ships again, this time with an armor made of Screaming Death scales, they managed to distract the hunters long enough for the riders to get to their dragons and escape. It was later revealed in "Snow Way Out" that Heather was actually acting as a spy. Only Astrid knew of this and kept it secret from Hiccup.

Dagur and Ryker then kidnapped Hiccup in "The Zippleback Experience". However, they were foiled by Barf and Belch.