All vampires possess a preternatural constitution that makes most normal damage inconsequential. Fortitude bestows a resilience and vigor far beyond even normal vampiric toughness. Kindred with this power ignore the mightiest punches and barely feel hails of bullets. This Discipline also helps protect against sources of damage even vampires fear, such as sunlight, fire and terminal falls.
Gangrel, Ravnos and Ventrue possess this potent ability. Gangrel enjoy the benefit of Fortitude as a matter of course, but Ravnos and especially Ventrue delight in the power's psychological effects. It's not unusual for a Ventrue to take a "fatal" blow, giving his opponent just enough time to register the vampire's smile before the Ventrue finishes off the shocked victim.
A character's rating in Fortitude adds to his Stamina for the purposes of soaking normal damage (bashing and lethal). A character with this Discipline may also use his dots in Fortitude to soak aggravated damage (Kindred cannot normally soak things like vampire bites, werewolf claws, magical effects, fire, sunlight or massive physical trauma). So a vampire with Fortitude 3 has three dice to soak aggravated damage.