You spit in the face of death.
Prerequisites: Half-orc or orc, ferocity racial trait, rage class feature.
Benefit: When raging, if you are hit by an attack that would deal enough hit points of damage to kill you (negative hit points equal to your Constitution score), as an immediate action you may expend 1 or more rounds of rage to negate some of this damage and keep yourself alive. Each round of rage you spend reduces the attack’s damage by your raging Constitution bonus, but cannot reduce the damage taken below 1 hit point.
For example, if you are raging, have a raging Constitution score of 18, are currently at 2 hit points, and are hit for 20 hit points of damage (which is enough to bring you to –18 hit points, killing you), you may spend 1 round of rage to reduce the damage by 4 (leaving you perilously close to death at –14 hit points); if you spend 5 rounds of rage, you reduce the damage to 1 (the minimum), leaving you with 1 hit point.