Well, after 19+ years of running my current campaign, the party finally had to tackle a group of trolls. Up to now, trolls were something encountered as a boogie man, something to frighten them into doing something or avoiding something. They rarely came face to face with more than one troll (or ogre mage) at a time, and avoided encounters with more than one using spells or simply walking away. Well, they could NOT avoid a group of trolls coming at them down the hall to investigate the combat occurring in the drow priestesses' chambers! This time we would see how well they fought trolls, especially without all their fire spells!
The curious thing about trolls is that regeneration is not well-defined in AD&D 1st edition. Trolls are also peculiar in that they don't start to regenerate until 3 rounds have elapsed since they were first damaged. Thereafter they regenerate damage at the rate of 3 hit points per round. It is assumed that death by normal blows (i.e. reduction to 0 hit points) does not kill a troll. The -10 rule for death introduced in the DMG should probably apply to them, but it just makes the math screwy when trying to deal with multiple trolls in a large encounter.
In the past, I've had any damage done to a troll reduce it as far as -10 hit points then stop. So long as the characters kept hitting them, they would thus remain down and unable to retaliate as oil was poured on them and lit. However, I don't believe that this was intended to be this way. Since 0 hit points was defined as death in the Player's Handbook, and the Monster Manual was written even before that, I assume that trolls should be brought no lower than 0 hit points. If you are able to reduce them that low in the initial first 3 rounds, then yes, you have a window of opportunity to soak them in oil (if handy) and light them up! Otherwise, they will revive each round thereafter until they can stand up from prone and kick your ass!
Now, the curious thing about fire and acid with trolls is that they cannot regenerate damage from those types. Does this mean that they take damage to their current AND full hit points? I think not. The act of burning a troll is meant to keep them dead. Hit points removed prior to the burning should not be counted. Thus if you get a troll to 0 hit points, then set them on fire, you are essentially keeping them from regenerating as you consume the body in flames. Otherwise you have to keep separate totals for each troll for normal damage vs. fire/acid damage. Now this can be done (it's a nightmare, but it can be tracked), but it seems that it would be impossible to do based on the rules for burning oil. According to the DMG, a single flask of oil burns for 2 rounds when used as a missile weapon. This causes 2d6 damage the first round, 1d6 damage the second round, and burns out by the third round. This seems fair for missile use, since there is a splash effect which disperses oil in a radius around the creature. Assuming that half the volume is thus lost in this manner, then pouring a flask of oil on the creature directly should allow it to burn for 4 rounds time instead of 2. Thus the troll above would be taking 2d6 damage the first round, and 1d6 damage for 3 rounds thereafter, for a total of 5d6 (or 5-30) points of damage. Now a troll has 6+6 Hit Dice. That's 6d8+6 hit points (or 12-54). As you can see, the average damage from fire (about 17 points) has no chance of fully destroying a troll (with average hp of 33). A DM could simply state that 2 oil flasks are required for each troll (dealing with averages only). However, I propose that a burning troll is prevented from regenerating once it is burned. So long as the oil is applied "post mortem" (aka at 0 hit points), then a single flask will consume the troll once it has taken 10 points of damage total (thus reducing it to -10 hit points and permanent death).
Rarely would a troll escape an encounter alive. However, in the situation my party found themselves in, they faced 7 trolls without fire spells (they're in the fire giant lair right now) or magic items (the magic-user burned out her wand of fire in the frost giant lair), and they came in with minimal oil for fear of being ignited by fire-using creatures (oh, Gary Gygax, you were an evil genius). Those trolls could have been much more since they were not encountered as a random encounter, but rather were fetched by the drow's accomplice in my plot as he escaped the initial death and mayhem meted out to the drow disciples of the priestess. The party only had enough oil with them to kill 5 of the trolls, the other 2 trolls left the scene after they witnessed the party burning their relatives alive! The party then left as quickly as they could, but even so they are far from civilization and are unable to get more oil flasks at this time. No doubt they will waste some of their spell selections on the next day with fire spells (and if I have anything to say about it, they would encounter only fire resistant fire giants and other monsters....).
The other strange thing about trolls is the fact that severed pieces will slither back together or continue to attack, if able, on their own. A funny picture in the original modules shows a dismembered troll hanging on with claws and fangs to a fighter trying to hack at it with a sword. Now this usually will not occur in AD&D. There are no hit location charts and damage is generic, not specific. The concept of the troll breaking into pieces with each hit probably stemmed from someone with a sword of sharpness or vorpal blade in the original dungeons run by Gygax. Without those two types of specific magic items, severing a troll's limbs cannot occur in normal combat! This is another case of one specific instance being applied universally in a confusing manner which makes it seem that it occurs more frequently than it does. One DM I ran with in the past assumed that troll parts separated from the whole will grow a whole new troll! Actually, the parts always seek to recombine with the original creature, so trolls cannot reproduce asexually in this manner. (This DM came up with a literal meat grinder for trolls.... a whole chamber was literally filled with regenerating troll parts...)
Also, trolls are not made of flash paper - simply touching a torch to a troll does not set it on fire any more than passing a finger through a candle flame would set a human on fire. Specific spells that state that they set things on fire are needed (such as burning hands, produce fire, flame strike or fireball). A good point to remember is that damage can be caused by fire without actually BEING on fire (skin blisters or ruptures), and is represented by a successful saving throw (if applicable). If a spell says it sets things on fire, and there is no saving throw, then you are on fire! Item saving throws are used to see if items carried are destroyed by the fire or are still salvageable.
So, regenerating trolls are confusing as hell! Having never dealt with by-the-book rules on regeneration and oil use before, this was sort of an eye opener for me. It took 3 weeks in the same 2 rooms for these "house rules" to be developed - once I saw how little damage burning oil did and the nature of troll hit points, I had to come up with a solution or the party would never get out of there!
