He did have some misgivings about his grandfather in Hell, but this potion had been checked by the Great Duke of Lavis Dukedom.
There was no issue with the medicine in itself. Marvin believed in the Great Duke's appraisal.
Marvin hesitated. The Archdevil Head's Divine Source was very precious and could only be used once. Generally, it would only be used when a Shapeshift Sorcerer could advance to Legend with it.
Although Marvin hadn't grasped any dual classing method and it was safe to say that getting a subclass to Legend rank was unlikely, it was still good to be prepared for an eventuality.
Thus, he decided to set aside the Divine Source Drop for when his Shapeshift Sorcerer class reached level 20.
But if he wanted to break through to the 3rd rank as a Shapeshift Sorcerer, he would need to use this potion.
Having made up his mind, he stopped to rest and found a safe place to take the potion.