Karl is of a long line of Alchemists stretching back many centuries into the Dark Ages and perhaps beyond. However, born the second of a set of twins, Karl never really took to the family art while his brother Konrad excelled at it. Prefering to go his own path and live a normal life, Karl went to college and became an inorganic chemist, a field in which he excelled for many decades. Over the years Karl fell out of touch with Konrad, and finally heard no more from him after 1974. Karl married, had three children, and retired shortly after his wife passed away from cancer.
Karl found retirement boring, and was at loose ends. Golf was a common pasttime, but an unsatisfying one. Then one day he received an unexpected package, and opened it to discover his brother's effects and an intriguing letter from a Doctor Allosius Jones explaining that Konrad had been a leader amongst a loose alliance of monster hunters, but had finally been slain by a master vampire. Karl had left such things behind him, but he knew enough of the Supernatural World and his brother's trade to believe it.
Among the effects was one of his brother's diaries describing his war on monsters, and a number of recipe books for Alchemical substances including a few that Karl recognized as being family heirlooms. To his suprise, Karl discovered that the old Alchemical scrawlings tickled his fancy like they never did when he was younger, and it wasn't long before he was bumbling around in his basement chemistry lab repurposing it for Alchemy. He puttered around for weeks and months, knocking the rust off his long disused early teachings.
Among the various books, Karl had found the recipe for a draught of long life, which the family had long taken advantage of. Knowing the efficacy of the draught, Karl worked tirelessly to master the technique and brew one for himself, and thus successfully extended his life. Though he took it so late that he is still an old man at least the toll of years has slowed to a crawl for him and in the intervening two decades since he took the draught he has barely aged half a year.
Relearning his family art occupied Karl for several years, but eventually he had become skilled enough that he itched to do something more. His grown children occassionally visited, and he still had a few old friends to socialize with on occassion, but Karl is the sort of man that needs more stimulation. Finally, on a whim, he wrote to Doctor Allosius Jones inquiring as to whether there were any more of his brother's effects to be had, and so forth. This led to an exchange of letters, then a phone conversation, and then a visit. Soon Karl was pulled into Doctor Jones' wide circle of acquaintances and became a source of Alchemical supplies, making a handsome but not unfair profit.
Eventually that too got boring, and Karl decided to take a more active hand, slowly and carefully but inevitably becoming a Hunter in his own right. So far he's found the experience exhilerating...and he's managed to harvest some useful alchemical components from fallen monsters in the process. Win win.