Dionysius was once a legendary adventurer. In his youth, he single-handedly defeated the troll invasion of Keldagrim. He crushed the enemies of one of the mountain tribes and taught the people of Karamja how to use powerful herbs that might aid them in battle. He committed great deeds throughout his life, and the world is a better place with him in it.
Or it was.
After he settled down, finishing his book on destructive magic, Dionysius began to feel that the world was a little unfair. He had tirelessly given his youth for the betterment of the world, and he had nothing to show for it. Even his devout faith in Saradomin wasn’t making his life more comfortable.
So, like so many do, he turned to crime. He targeted the nearby bank, his magic making quick work of their security, and he lifted himself a great deal of gold as well as a snazzy blue party hat. Content to consider this repayment for saving the world so often, he now sits back and enjoys his well-earned wealth.
The Temple Knights consider him an ultraviolet archangel threat and watch him very closely... from very far away.