Archvale

Along the game you will find an item by itself in a room called a “Mega Plum” to increase the strength of your health potions. For this achievement however, you only need one.

Once you reach the second town in the game, “Fairreach,” you will find in the stop type area there will be a frog stirring a pot. Talk to him to give him the plum to increase your potion strength and the achievement will pop.