Healing was a very competitive field but due to Eberhartt's unreasonably high fees and his dark personality, he tended to have far fewer customers than others doing the same work. In fact, he didn't talk to any other healers aside from Doctor Bertrand Wirtz, with whom he shared a scholarly passion for unconventional medicine, causing them to spend long hours discussing research, scientific disputes, and consulting with each other on difficult patient cases. The two would also frequently ride off to Wirtz's village residence where they claimed to be working on something groundbreaking. The truth was that they were experimenting on werewolves to find a cure for lycanthropy.
Indeed, Eberhartt was very interested in lycanthropy as a whole and always looked for a solution to this peculiarity as he was a werewolf himself, having been turned into one when he was 20 years old while in his fourth year at Ban Ard Academy. When this occurred, the school's masters decided to use him as an experimental guinea pig but he managed to flee.
After an untold number of years, he finally settled in Novigrad where he found it easy to blend in and, together with Wirtz, he discovered a medicament that stopped the physical transformation. Nevertheless, he still had attacks of madness and bloodthirst during the full moon and thus confined himself to his residence during this time, keeping himself chained to a bed with a throat full of sleeping pills and with dwarven mercenaries guarding over him.