Over the course of many battles, you have to learn about how to hit your enemies where it hurts and deliver crippling blows. Now when you make a critical hit with a melee attack, the target of your attack suffers a –2 penalty to both their attack rolls and AC for the rest of the encounter. This can only be applied once to a target during an encounter and does not stack.
[Conversion of the Triumphant Attack feat from PH of 4e to 5e]
Comments