You clear your mind of all distracting thoughts and allow yourself to focus your mind on the fight at hand allowing you to see opertunites in an enemies form for an opening. In practice this gives you advantage on ability checks and allows you to score a critical hit on attack rolls of 19 when cast at 6th level, 18 when cast at 7th level, 17 when cast at 8th level, and 16 when cast at 9th level.