Revised because the first version sucked. :)
Their first week at sea taught the riders a lot, unfortunately, they also learned that they all got seasick.
"'Ere" said the sailor running the sickbay on the day they finally told Captain Scott about getting seasick "Drink this, it'll make ye right."
Each of the riders eagerly quaffed down the medicine, which tasted terrible, now that you mention it.
Within an hour they were back to helping out the crew, working their assigned posts, and increasingly noticing Adrian's sour mood towards them.
Sixth Day at Sea… As Hiccup and Astrid climbed the stairs to the main deck that morning they could hear an argument taking place, peeking out between two barrels they saw Adrian and Captain Scott arguing.
"But Captain, they're Drachen! You shouldn't have them onboard!" shouts Adrian
"I'm well aware of that Adrian, but these un's seem to mean no harm." Said Scott
"But Captain…"
"No, Adrian. I've heard enough, they're me crew now and that's final!"
Adrian walked off with a huff, and as he passed and saw the two Dragon Riders he gave them a venomous glare.
Hiccup and Astrid decided that they had to convince Adrian somehow that the Dragons meant him no harm.
So, the next day, when Adrian was in the hold checking for leaks (and rats) they joined him…
"What'd you two want?" said Adrian
"Captain Scott ordered us to help check for leaks with you" said Astrid
"Fine!" Adrian said, throwing up his hands in exasperation
"Adrian" said Hiccup, a few minutes later
"Hmm…" said Adrian
"You know, the Dragons weren't always our friends." Said Hiccup
Adrian looked up, his features hardened, and said "Oh really?"
"Yep" said Hiccup "Five years ago we were killing them, they raided our village at night and we killed as many as we could."
This story seemed to catch Adrian's interest "Then how'd you make friends with the beasts?" he said
"Well" said Hiccup "If you look at Toothless you'll see one tailfin is ripped off, that happened when I shot him down. After that I tried to kill him, and well, he just looked so scared, then I freed him."
"He could'av killed ya." Said Adrian
"But he didn't. Then I began to train him, I made him a prosthetic tail fin and we found out that the dragons only raided our village because they were enslaved by a dragon bigger than this ship. Our tribe assaulted the dragon and me and Toothless killed her, we shot a plasma blast into her throat and she exploded. I lost my leg in the inferno, Toothless using his wings to shield me from the flames. They've been our friends ever since." finished Hiccup
Adrian was silent for a minute, and finally said "I'll admit that your Drachen don't look like the one we saw in Eisen, that that Legion dammed Vampir rode!"
"Vampir?" asked Astrid, flummoxed
Adrian sighed "Well, you've told me your story, it's only fair I tell you mine."
Hiccup and Astrid sat on a pair of upended barrels and waited.
"It started five years ago, in The Walder…
Five years ago… Adrian was traveling with a family traveling from Freiburg to Stutzung, they had just bedded down for the night when five Revenants loped out of the darkness an attacked them, behind them waited a dark figure astride a black stallion.
Adrian, trained by his father, who was a veteran of the War of the Cross, was being attacked by two, and just as he managed to run his saber through the chest of the bigger one he heard a piercing scream.
He turned about to see the father of the family, William, impaled on the claw of a revenant, who was in turn impaled on William's sword. Which happened first, Adrian never found out.
However, that wasn't what made William's wife scream, the dark figure on the stallion had waltzed into the clearing and grabbed their daughter Ramona by the throat. He was a Vampir, you could tell by the bloodless pallor of its skin and the sharp fangs.
Adrian launched himself at the creature, only to be awakened an hour later by William's wife, who had managed to limp away as the Vampir kidnapped her daughter. Then and there Adrian vowed to her to kill the creature and rescue Ramona.
Five months later… Adrian was in shambles, he knew where Ramona was, but had no ability to assault Castle Drachen. It was here, in a seedy tavern in Adel, that Captain Scott found Adrian and offered his crew and ship to killing the undead horrors of Castle Drachen.
However when they stormed the castle, by way of a underground passage that an escaped slave had told them of with his dying words, they found the Vampir riding not a stallion, but a Drachen!
Only a lucky shot from a commandeered fortress cannon managed to fell the beast after it killed Scott's Master-at-Arms, and several other crewmembers. Adrian then chased the Vampir into its crumbling castle and staked it a hairsbreadth away from sucking Ramona dry.
Present Day… and after I returned her to her mother I joined Scott's crew, in payment for their help." finished Adrian.
Hiccup and Astrid were both silent, Hiccup then eventually saying "I'm sorry, but… well, I don't know, maybe that Vampir took over the Dragon's mind, we saw it with the big dragon we called the Red Death. Maybe it was just as much a slave as the man who told you about the underground passage."
"I guess, but still… it's hard to forget." Said Adrian
Hiccup smiled and said "We could help you with that"
Next thing Adrian knew he was sitting behind Hiccup on Toothless as they shot into the sky, by the time of landing Adrian was smiling, something that when Captain Scott saw it he said that he hadn't seen Adrian do since he joined the crew.
So that night, as Hiccup slipped into his hammock he felt a nudge on his shoulder, and looked over to see Adrian, who then whispered "Thank you"
Hiccup just smiled and nodded, before rolling over and falling asleep
As Adrian lay in his own hammock he finally fell asleep, happy, and at peace with his troubled past…