Every year, a few people tried to break into the dungeon, because there were tales told about great treasure in there. None of them ever seemed to come back, though.
One day, a young man decided to laugh in the face of danger and brave the dungeon. He went along with a few other people, who were all planning to cheat each other out of the fortune that lay within the strongly protected walls. They climbed down far into the dungeon, hopping over the spikes and ducking under dart traps. Soon, the young man and someone else stumbled upon treasure. He took it all for himself, and when the other person asked for some of it, he refused. The woman he was searching with attempted to take some of it, and then the young man killed her.
This act of desperate greed disgusted the dungeon guardian, and it attempted to kill the young man. He barely escaped death, but with a price. He would be trapped forever at the dungeon, stopping people from doing what he had done. Many years later, he grew old and lost almost all hope, filled with regret. One evening, though, a slightly arrogant hero boasted of how he could beat the old man's master. The old man summoned his master, but while doing that, got killed.