Grievous Wounds

Occasionally, battle can leave lasting scars on those in the fight. Upon landing a critical hit against a medium or smaller creature (This includes critical hits granted by enhanced critical or other abilities), if that hit deals 25% of the target creature's maximum Hit points or more in piercing, bludgeoning, or slashing damage, a grievous wound is inflicted.

The attacker can choose to cripple a creature's limb (excluding the head), depriving the creature use of that limb. In that circumstances, the target creature must make a Constitution saving throw with a DC equal to 10+50% of the damage taken (up to a current maximum of DC18). On a failed save, the target creature's limb is crippled. This can vary from a broken arm (bludgeoning damage) or a completely severed limb (slashing damage).

Occasionally, certain other damage types can cause crippling wounds, varying upon the type of attack. Such an attack based upon psychic damage for example could cause disorientation or a large amount of stress damage. A cold-based attack could freeze and shatter a limb.

In any event, a crippled limb is considered unusable in combat. Any action that would require full use of the limb is disabled (For example a creature that is granted the multi-attack benefit from having multiple limbs would lose the benefit of that limb), and actions requiring partial use of the limb are taken at disadvantage. Barbarians can ignore the effects of a crippled limb while actively raging, but will still have to contend with effects of the limb after the rage ends.

Extensive medical care can heal a limb back to full effectiveness (certain spells and effects can be used to instantly or rapidly regenerate lost or damage limbs). In the short term, healing magic can be used to repair a critically damaged limb by focusing the magic on the limb alone. In order to repair the limb fully, the entire amount of hit-points lost (due to the hit that severed the limb). Restoring these lost hit-points in this manner does NOT replenish lost hit-points to the character's hit-point total.