If Renfield didn't have bad luck, he would have no luck at all. Living a mostly feckless life, he ended up orphaned at a young age. Living off the land he learned to forage, and fend for himself. It was during one of those foraging outings, Renfield was asleep, and a camp invader quietly visited. Little did he know who was laying there.
As the visitor approached, Renfield awakened with a start. Pitifully groveling and pathetically begging for his life in hopes to gain pity. As was Renfields luck, pity wasn't the emotion the visitor felt. Disgust was closer, but he had to feed. But instead of killing the feckless fool, he cursed him. Not only did he let him live, he left him with the craven taste for insects, cockroaches being a particular favorite due to their texture, their crunch.
The visitor wiped the blood off his lips as Renfield lay there, even spitting a bit out. Sometimes, blood sates the need, but is not a delicious meal. Changing into a bat, the visitor left Renfield laying there, 2 holes in his neck, maniacally laughing at his new fate.
The new species he had become had its benefits. The ability to climb surfaces helped him gain experience as a Ranger. His sense of smell, and connection with the grave made him eerily better at his job. Learning to corrupt his goodberry spell to create cockroaches instead of fruit made him a lascivious fool who like nothing more then to summon a handful and eat them in front of people to see them recoil in disgust. And then, there was his laugh wiht those wide eyes.... that maniacal, cheesy, insane laugh..........