When you attack with a melee weapon, you have the option to roll a d10 dice.
If it lands on an even number, the enemy you attacked will take 1d4 bonus damage. This increases by one die every 4 levels. If it lands on odd, you take d4 damage.
However, whatever happens, you can roll a d10 dice again. If it lands on even again, the enemy gets stunned and loses their next turn. If you got an even roll, roll again, and it lands on odd, the enemy gets an opportunity attack on you. If you get an odd roll, reroll, then land on even, you gain back the HP you took. If you get two odds in a row, you get stunned and lose your next turn.
You can choose to not roll again after the first time.
Comments