It took a while for them to calm down and the girl in purple to explain. The sword was the previous possession of their king. He held it while conquering worlds, but once the battles were done and their people were the strongest in the galaxy, he sealed up the sword, knowing that it was a sword of bad luck and ill omen. Even with that being the case, buried secrets don't stay buried forever and enemies from outside their realm came looking for it. With their search, they brought destruction to their people and their empire which fell in a matter of days to these strange wanderers of the stars. Their leader, long knowing that something like this might happen, had planned for many long years and using lost and ancient knowledge, created this fortress to safeguard a small group of their people to at least ensure their race didn't die out entirely.