Blizzard

Two of these can be crafted at any one time and placed in the consumables slot.

"Witchers usually drink the Blizzard potion immediately before combat. The potion is also favored in especially dangerous situations."

Blizzard is one of the most powerful witchers' potions; it improves reflexes and reaction time, allowing a witcher to better parry and evade attacks. It slows down time, making Geralt's movement and everything else slower.