"Two reasons really." Omorgal said to Aqua's question. "Firstly, if I told you that there was a creature out there with five heads and three legs that does a rain dance whenever it gets mad you probably wouldn't believe me. By your logic however you should believe me if I had also told it had scales. Now think about it. I've never seen a dragon in my life until a few moments ago. The biggest scaled creature I've ever seen was another dragonborn like me and he wasn't much bigger than I am. Why should I have believed that there exists a giant winged lizard which supposedly can also breath fire? And why should the fact that it had scales have made any difference? Sorry to say this. but the being you are just didn't make sense to me. Dragons to me were creatures out of legends, legends I didn't believe in."
Speaking of legends. They are the second reason I didn't believe you were real. Because even if they were true, the legends state that your kind died out. It's a bit of a long story however, it may not be the best moment to tell it.
Omorgal looked at the door thinking of a way to get it open. Brute force was of course an option with a big dragon to deliver it but the dragonborn thought a little finesse might be better here. Looking at one of the edges of the door he got an idea. He opened his bag and took out his blade of dancing heat. "You said I would be able to yield this blade with great effect." He said to Aqua. "Let's see if you're right." He tried putting the blade into the split between door and wall on the side where the lock should be. It didn't fit. Realizing that that side wasn't going to work Omorgal tried the other slit. Luckily there was enough of a gap to fit the blade through and as he moved the blade up and down it got blocked on several places telling the dragonborn where the hinges were. Now placing the blade above the highest hinge Omorgal made the blade red hot. Then he tried to slowly move it down, hoping it would slowly cut through the hinge or failing that: melt it away. "Yes!" He said after noticing his plan worked. "This is going to take some time." He told Aqua. "Looks like I've got time to tell that legend I was talking about earlier while I do this."
"You see, legend says that the ancestors of my people, so including my ancestors, were once human. They lived in a city and worshiped their gods in their temple. One of these gods was depicted as a dragon. One day a dragon appeared near the city and because he could have been sent by the dragon god the high mage priest was sent out to investigate. When the high mage priest came back he told the city that the dragon's name was Vermis. Vermis, he said, was a refugee who had fled the killing of his species and was now the last of his kind. Vermis had asked the high mage priest for shelter and protection and because the dragon was a holy beast the high mage priest had agreed . He had promised Vermis that he could live in the temple since that was a fitting place for a holy beast and also the only building in the city the dragon could fit in. The city agreed with the high mage priest and a huge feast was thrown to celebrate the occasion."
Suddenly the blade shot downward having cut through the first hinge and losing its resistance. Still red hot Omorgal pulled it out of the slit and looked if it was damaged. "Years past and the inhabitants of the city had stopped worshiping most gods only paying respect to the dragon god and its representative in this world: Vermis, who had taken on this role when he moved in. A special temple guard had been formed out of men and women who wore armor decorated with scales and masks that looked like the head of a dragon. It was around this time that Vermis started to ask for offerings promising blessings for the city in return. At first it were little things, a bit of food, a piece of jewelry but things accelerated quickly to its logical conclusion: virgins."
Omorgal saw no damage on the blade. Putting it in he started with the second hinge. "The first virgin was given without protest, the city thought she would become a priestess of sort and saw it as an honor. In fact, the city had volunteers compete for the honor. But the lucky volunteer was never seen again and when Vermis asked for another virgin there were no volunteers. The city had to choose one for the temple guards to drag into the temple. But Vermis wanted still more and started to ask for certain virgins. And when he finally asked for a noble's daughter the city refused. Mad Vermis burnt the city hall and threatened to curse the city with his god's might if he didn't get her. Seeing no choice the city gave her to him. After this Vermis simply took what he wanted and he and his temple guard, who were often sent to fetch whatever their lord desired, were feared and detested by all. Only the mage priests still supported him."
The second hinge gave away and Omorgal started with the third. "Finally the city had enough and revolted. Mad again Vermis burned whole neighborhoods to the ground while the temple guard killed everyone in the street. The temple guard were up against a foe that was greater in numbers than they were and which fought ferociously and were beaten back to the temple. Seeing this Vermis helped his servants by strengthening them with a 'blessing' as he called it. Blessed the temple guard threw itself into the fight again and they succeeded in beating down the revolt. Relieved the fighting was over they looked at each other clearly for the first time since the fighting had begun and each of them saw what you are seeing right now. A dragonborn, half human, half dragon. Vermis 'blessing' had changed them. Because their armor and mask looked so similar they hadn't noticed sooner. Angry the leader of the temple guard demanded Vermis to turn them back into humans. Vermis refused saying that this was his blessing and that the temple guard should be grateful for what he had done. Feeling betrayed the former temple guard now dragonborns attacked Vermis who fled to his temple, unable to withstand his one creations. The dragonborns then stormed the temple killing the mage priests and fighting Vermis in his own temple in a bloody battle. And there they killed the last dragon of this world before the statue of the dragon god."
The third hinge now cut through Omorgal started with the last one. "The city was a ruin because of the battle and was never rebuilt. Knowing what they were and what they had done the dragonborns knew they couldn't they couldn't join up with the other survivors of Vermis rule. Instead they left the city and built a small village far away from their former home. And it is of these dragonborn that I descend."
Finishing telling his legend Omorgal cut through the last hinge. The door, now without its hinges, was still there but it should be removed quite easily. The dragonborn pulled his blade out of the slit and made it slowly cool in his hand. "According to this legend at least. I've never believed it but seeing that you exist there must be some truth to it. You know now why I, even if I believed in the legends, couldn't believe that you were real. Now you also know why I couldn't trust you. Vermis, if he really existed, betrayed my people and he was a dragon. You are also a dragon, I had to be careful." Putting the blade away he looked at the door. "By the way, you should be able to open it now."