Typically used with: Endurance.
In short: stay healthy. The Vitality skill is used when a character is fighting off disease, poisons, tranquilizers, and sickness. This skill essentially represents your ability to flex your immune system and physical composure. If you want to get on all of the carnival rides, even the spinning ones, Vitality is for you.
A character heals an amount of HP equal to the sum of their Endurance and Vitality for each full night of rest. No roll is required.
You can make a Vitality check to ward off disease. Each source of infection has its own DL — the higher the DL, the more virulent the infection. Some diseases are spread through touch, others through injury and direct contact with the blood, and others still are airborne.
If you meet or exceed the DL, you remain healthy. Otherwise, you gain the infected condition and assume Knockout penalties (see the "Diseases" entry in the Damage and Death section of Chapter 4: Life and Death). Every day you remain infected in-game, you have to make another Vitality check. If you succeed, you may ignore the effects of the disease for one day. If the player makes two consecutive, successful checks she is considered to have beaten the disease. Rare diseases might only be curable with medicine, if a cure is even possible.
Characters can use the Craft skill to create medicine that helps your immune system fight off infection.
You can also make a Vitality check to tough out poison. Each poisonous substance has its own DL — the higher the DL, the more toxic the poison. Some poisons enter the bloodstream through injury, some must be imbibed, and some can simply be absorbed through contact with the skin.
If you meet or exceed the DL, you resist the poison. Otherwise, you gain the poisoned condition and begin taking a set amount of damage every round (see the "Poisons" entry in the Damage and Death section of Chapter 4: Life and Death). Each round you remain poisoned, you make an additional Vitality check. If you succeed, you can ignore the effects of the poison for that round. Each poison has a set duration.
Characters can use the Craft skill to create an antidote, antitoxin, or antivenom capable of counteracting the poison coursing through your veins.
Vitality is also used in those unfortunate situations where your character needs to keep his lunch down or his pants stain-free. The higher the DL, the more likely you'll be sick. You might need to shrug off seasickness, airsickness, or motion sickness. Someone may have replaced your milkshake with chocolate laxatives. Whatever the case, if you fail the check, you move one step down the Knockout Track. If the conditions persist (and they usually do), you need to make subsequent Vitality checks. Your GM can tell you if that's every round, minute, or hour. Each additional failure puts you another step down the Knockout Track while you're "shouting groceries" in the corner.
Certain spells call for a Vitality check to resist, for instance Disease, Poison, and Sicken. In this case, you may add any points in Magic Defense to this roll. The mage makes a Casting Roll. You make a Vitality check. If your result meets or exceeds the Casting Roll, you elude the effects of the spell.