The biological process of Regeneration is a wonderful thing that never ceases to amaze me. Why some creatures and not others? Surely this would be a wonderful trait in just about any prey creature, no? Sacrifice a limb to your predator, and away you go. Mostly, just like new, back to normal. Sometimes, not.
And then there is the troll. A creature who lives for combat and violence [Sidebar: I especially like the history of the Uz, or trolls, in the Runequest world. While they do not regenerate, as a rule, they are creatures who have come to embrace a sort of racial anger and hatred of all others - especially surface races such as men and elves. The anger comes from repeated cursing from the gods, which has left the Uz race to not breed true, to bear mutated children, and to remain stunted and stupid as a species. Certainly, these are all reasons to embrace violence. And professional wrestling.] and who inhabits forgotten locales of the world (above and below the surface) that are prone to accumulate wonders and treasures, will not doubt sooner or later have a run in with well armed adventurers of all sorts. These leads to what would otherwise be a nice meal, rather to an exercise in getting one's own limbs chopped off. Repeatedly. Over time, you could see how regeneration would be a useful survival trait here.
Most trolls (of the D&D and related family of games) have a standard sort of trollish regeneration that is something like 3 hit points per round, starting with the third round after damage is accumulated. Some of the subspecies of troll actually have higher rates of regeneration - how about 6 points per round, beginning with the fourth round. Or how about 10 points per round for a Fire Troll, whenever it is immersed in lava or magma. I'll take two of those, wrapped for travel, please.
If you remove a body part of a troll (easy to do with a Sword of Sharpness, a Vorpal Weapon, or certain Lawn Implements), it will eventually begin regenerating on its own. Several versions of several games have had different points of view on this, but I like the fact that every arm and leg will grow into a new troll, or find a way to rejoin it's sibling limbs.
Does being regenerative lead the troll to be more fearless? Sure having your hand burnt or slashed or chewed off hurts, but you can always grow a new piece. This leads me to an interesting point. Using a firebrand or acidic blade to fight a troll is all well and good, but it does not keep the parts from regenerating. Sure it might slow the process down, but unless you completely destroy the inanimate parts with fire or acid, then the scorched or burnt parts will eventually rot off, and the clean tissue underneath will begin regenerating again. It is a beautiful machine, the troll.
As dungeon denizens, I can think of none better. They have a (admittedly rudimentary) intelligence - enough to be given items to occasionally use (armor, weapons), they can be crossbred with any number of other species (giants, ogres, goblinoids, man, etc) for interesting results, and is terribly receptive to magical mutation. Perhaps all of these traits trace back to the regeneration ability? The implications are certainly there. And how do you starve a troll? They will eat anything. Anything. In times of desperation or hunger, presumably this means torn and shredded parts of themselves. And after eons of living in some stony vault deep beneath a mad wizard's tower, the troll might (having consumed his own limbs many hundreds of times over) occasionally cry out to dark forces of the night in desperation or madness. More on that later...
In practical terms, I prefer to just keep a running total of the damage on the troll, where I add in the damage done each round by the players, then subtract the regeneration bit. If a troll were allied to somewhat smarter beings, they might employ it somehow where it could bottleneck a trapped foe, such that only one or two of the trapped party might attack the troll, giving its regeneration a sustained chance at keeping the troll alive long enough to harass the party.
One thing to point out is that the presence of the dreaded grey troll leads us to presume that not only Physical damage can be regenerated by the troll's amazing physique. The grey troll is what results when a normal troll is subjected to the level drain (by undead, or other) and is drained to the point of death. Later on, the whole body regenerates back the lost "part" - soul, spirit, lifespark, animus - yet is now not entirely sane nor of its own faculties. The regenerated troll understands enough that it realizes that it has died - at the hand of some supernatural being - and wants to gain vengeance since it (the troll) has now regenerated back to "life".
Magic Item - Trollblood Mail - this is a magic armor made by a certain tribe of Duergar to aid in their ongoing battle against a large clan of trolls. The mail shirt is a +2 hauberk of chainmail that magically sizes to fit any humanoid torso that attempts to wear it. Once worn, the magic of the shirt begins to affect the wearer, however. The wearer starts gaining a +1 to his constitution, once per week (cumulative). With this bonus, the physiology of the wearer begins to approach that of a troll - faint greyish-green rubberiness of the skin, the thickening and darkening of the blood, etc. Once the constitution reaches 21, the change is complete and the character has some outward trollish marks. Also, a regenerative ability is gained, of 1 HP per 10 minutes - which is usually associated with a constitution of 25, but is conferred by the magic in the mail. This item is usually only reserved for the most devout and dedicated of duergar fighters, as the effects are not reversible (nor is the shirt removable) without a wish.
Tags: trolls, regeneration