When the player is on a ¼ of their health, if they land a combat roll of 18+, they initiate a critical strike. This increases damage by +4 and with a chance of inflicting a wound:                              Roll D10:

Blood loss - 1 - 4: Loses 1 HP per turn for the rest of the fight. Can be healed with basic healing magic but not potions.

Limb Cripple - 5 - 8: The opponent has all their saving throws (excluding Wisdom and Intelligence) reduced by 2. They also have their speed reduced by 10.

Blind 9: The enemy has their saving throws reduced by 3. They also have their combat rolls reduced by 3. 

Concuss 10: The enemy is stunned for the next 3 turns. This stops them from doing any action.

Upon activation, Roll D20, if the number is 1 - 10:

The player is stunned for the next 1 turn.

If the number is 11 - 20:

The Player gains 3HP(if not full health) and +2 on their next combat roll. Can be used once per hour.

On use, gain temporary hp based on constitution + strength modifier. Can be used once per long rest.