The achievement unlocks when you create a potion, either through experimentation or by using a recipe, where the Essence of Fate is one of the components. All potions that include Essence of Fate as an ingredient are master recipes. In order to make a master recipe, you must be at level 5 in the alchemy skill or higher. Moreover, you cannot use the Essence of Fate in recipes until you complete the fifth main story quest—The Coming Storm. The four quests that precede it are Out of the Darkness, Into the Light, Old Friends/New Foes, & The Hunters Hunted.
As a reward for completing The Coming Storm, you receive the recipe for Fate Potion. It uses 4 Essences of Fate that are frequently picked up as enemy drops when you defeat them by invoking reckoning mode. Since completing The Coming Storm unlocks your ability to use the Essence of Fate in making potions AND gives you a recipe that includes it as an ingredient, the simplest way to unlock the achievement is to go to an alchemical lab and create a Fate Potion. This assumes you have alchemy skill level 5 or higher and you have acquired four or more Essences of Fate.
Naturally, any potion with Essence of Fate as an ingredient counts for the achievement. As a rule of thumb, a journeyman recipe (three ingredients) that creates a 'greater' potion can produce the corresponding master level potion by adding an Essence of Fate as a fourth ingredient. For example, a Greater Healing Potion is made by combining the following three ingredients: 3X Black Cohosh, 2X Embereyes, and 1X Bloodroot. When you experiment and use those three ingredients with Essence of Fate as a fourth ingredient, you will create a Master Healing Potion and will pop the achievement (if not previously unlocked).