Vincent's alchemy skill is something that he has taken note of after he managed to cure Dennise of a disease that he would even have a hard time healing.
Based on the symptoms that the Divine Doctor had seen from Dennise, he already guessed that it was called Tantra's Chill. It's a disease that slowly drains the infected person's life.
If it was him, he would need various precious herbs to create a potion to alleviate the symptoms before he can use his healing hands. However, he had seen Vincent use a simple mid-grade potion that seems to have been slightly modified to completely cure her without any side effects.
It was something that he couldn't understand and wanted to learn! However, this is obviously Vincent's secret and he can't just ask for it without paying a huge price.
It's similar to the secrets of his healing hands. There was no way he would easily reveal its secrets as this is how he makes a living.
