The Defenders of the Wing King Trials are a set of three trials that a person must pass in order to become the King of the Defenders of the Wing.
It is unknown when the Trials were created, but the practice is very much apart of the Defenders of the Wings customs.
Near the end of "Defenders of the Wing, Part 2", Snotlout learns he must take part in the Defenders of the Wing King’s Trials before he can become king. As Throk shows Snotlout the Pool of Valor (a pool filled with lava), Snotlout chickens out, retreating back to Hookfang in order to escape. Leaving Mala stunned.
In "Saving Shattermaster", The Riders are summoned to Caldera Cay, where Mala sets up the Trials for Snotlout. At first Snotlout tries to flee, but after being egged on by the Twins who expect him to fail, he decides to compete to prove he can. Much to the surprise of the Twins, Astrid, and Fishlegs, Snotlout shows bravery and completes the Pool of Valor and the Maze of Poisonous Eels. He even had to save Fishlegs, who fell into the Maze from Giant Eels. By the third trial, however, he is sabotaged and just misses taking an arrow for the Queen, thus failing the Trials. He is, however, thrown a feast and is King for a Day for his effort.
Sometime between "Chain of Command" and "Mi Amore Wing", Dagur successfully completed the King’s Trials. He appears on Dragon's Edge with an arrow sticking out of his back to tell the Riders he and Mala are getting married, making Dagur King of the Defenders of the Wing.
The Pool of Valor
The first trial requires the participant to walk across a pool of lava, with only burning rocks formed by the Eruptodon as a path. If successful in crossing the lava pool, the participant moves on to the next test.
Maze of Poisonous Eels
The second trial requires the participant to guide themselves to the exit of a maze, littered with poisonous eels. The participant is also allowed to bring a weapon if desired. The maze itself is filled with waist-deep water and towards the end there is significantly more eels of different sizes. If the participant is successful in reaching the end, they move on to the third and final test.
The third and final trial is rather simple. The participant must use themselves as a human shield before an arrow can strike the Queen. If successful (and alive) the participant would have become the new Defenders of the Wing’s King.