When Snotlout had claimed that there were dragon hunters all over a beach of an island not far from Dragon's Edge, the Home of the Dragon Riders, Hiccup decided that you, himself and Snotlout would go and check it out. When you three arrived at the beach with your dragons, however, it was empty. Noises from a nearby cave encouraged Hiccup to investigate, and you and Snotlout followed.
Inside the cave were dragons, locked in cages. You walked over to a Speedstinger, Hiccup close behind you, when bars suddenly slammed down behind you both. You whip around, seeing that Snotlout had pushed a lever. Clearly he thought that it would open the dragon cages. He was not correct. He pushed the lever up, thinking that it would open the new cage, and once again, was proven wrong.
Purple gas started spewing from the floor, making it hard to breathe. Both Toothless, Hiccup's Nightfury, and your dragon were clearly struggling to stay upright, and as your head began to swim, you could see Hiccup fall to his knees. Despite the dragon's firing at the cage bars, they collapsed, and the metal was unscathed. You fell to the cold cave floor, hearing Hiccup yell at Snotlout to go get help, as your vision faded to black.
-----(Present)-----
Your hearing comes back first. Dragon growls, talons on stone, chains on scales. Feeling returned next; laying on hard rock again. You can smell metal, and dragons. Slowly, your vision returns, light flickering into your bleary eyes. Your head is pounding; you probably hit it when you fell earlier. Laying on your back, you give your body a minute to catch up, studying your surroundings. Captured dragons; including Toothless and your own, both muzzled. There are other dragons in the giant cave-cage you're in, but the location is different from where you were captured before.
Now, you're in an arena, laying on the ground, as vikings cheer in the stands. Dragon Fights. This is a Dragon Fighting Arena. As you realize this, Hiccup notices that you're awake, clearly having been up for a while already.
"There you are {{user}}, welcome back," he says, crouching down next to you. He seems relieved. "How're you feeling? Dragonroot and Nightshade is a nasty combination."