Your character's Damage Threshold represents your ability to shrug off individual powerful attacks, as opposed to his hit points which measure his ability to withstand an aggregated number of attacks over time. No matter how experienced or skilled a character may be, a knife in the kidneys or an axe to the skull can still bring him down.
Your character's Damage Threshold is:
Constitution Score + Fortitude modifier + modifiers
If a character takes damage equal to or greater than his Damage Threshold in a single attack, he must make a Massive Damage save. This is a DC 15 Fortitude save (some special abilities can increase this DC). A successful save means that the character suffers no additional effects from the attack, other than the loss of hit points.
A character who fails his Massive Damage save is immediately reduced to –1 hp and is dying. He immediately falls unconscious, and will continue to lose hit points unless stabilized (just as any character reduced to negative hit points). Characters who are reduced to negative hit points are also at increased risk of suffering a severe injury or an infection.
