From Neversummer 4 Wiki

Implemented, amazingly useful for high-dex characters when fighting one or two creatures at a time.

NOTE: The engine is capped at 3 parries per round and you won't parry the first three attack made against you each round, you will seemingly parry one attack per "attack phase" for lack of a better word. When making a full round attack action, your number of attacks per round are divided into three phases. If you have 4 attacks per round, your attack pattern will be, 2 attacks, 1 attack, 1