Mastermind Potion Quest/Spoiler

Spoiler:
Go to the Formogar Mines:



Then follow this path:



Warning: You can meet a Nightmare which spawns on 3rd floor (marked with a small square).

You will find a reward in box, near the wall.

There is also a second potion to obtain. Go back to the enterance and follow this path:



Reward is in the box, near the fire.