In GURPS there are three forms of damage: basic damage, penetrating damage, and injury. Basic damage is the amount rolled on the dice for the attack, penetrating damage is the amount after applying Damage Resistance and other protections (e.g., Injury Tolerance), and injury is the total amount of hit points you suffered from that attack. Seems easy right? Well, it can get complicated when you start adding in exotic protective advantages. But what happens if we start mucking around with that in-between stage that exists in the middle of penetrating damage and injury? Something interesting it turns out.
Theoretically, you could just buy more HP to deal with the splash over injury – but there may be a limit on how much additional HP can be bought in the campaign and there comes a point when more HP doesn’t make sense. Kromm posted an interesting new advantage a while back called “Vitality Reserve” (I’ve since used it and put it into Pyramid because it’s a damn useful trait). I’ve reprinted the text from the link below:
Consider adapting the Energy Reserve idea to HP instead of to FP. A “Vitality Reserve” should do what you want. To fully parallel the behavior of ER, it should be depleted independently of HP, not be subject to the ill effects of HP loss, heal in parallel with HP, and heal irrespective of rest. So VR would amount to HP that you can lose without shock, knockdown, knockout, or death, and that regenerate at the rate of 1 HP/day on a successful HT roll, regardless of conditions. Most of these advantages parallel Ablative DR (which is also independent of HP and not subject to the ill effects of HP loss). Moreover, neither affects what happens in slams and falls. The differences:
Advantages of Ablative DR:
1. Stops damage, not injury; e.g., 1 point prevents 2 HP of injury from an impaling wound to the torso, 4 HP of injury from a skull hit, etc.
Advantages of Vitality Reserve:
1. Soaks all injury, including that from disease, poison, and radiation; extreme dehydration and starvation; critical failures that result in direct injury; vampiric leeching; and Cosmic attacks that ignore DR.
2. Can be spent like HP for any ability that allows this, notably spells.
I’d say that justifies simply pricing VR like HP, much as ER is priced like FP.
Basic Damage – Damage Resistance = Penetrating Damage x Wound Multiplier = Injury – HP = Total HP lost
Basic Damage – Damage Resistance = Penetrating Damage x Wound Multiplier = Injury – VR = Remaining Injury – HP = Total HP lost
Basic Damage – Damage Resistance = Penetrating Damage x Wound Multiplier = Injury – VR = Remaining Injury – Injury Resistance = Final Injury – HP = Total HP lost