One of the biggest sticking points of 3.5 D&D is the versimilitude of character advancement for NPCs. As an illustrative example, consider a randomly-generated 12th-level commoner. Any metropolis-sized city generated by the rules set forth in the DMG is virtually guaranteed to have at least one such individual. Immediately the question arises: how did this individual come to be?
By the rules as written, Bob the Commoner would have had to have taken part in at least 156 on-level encounters in order to accrue that much experience. While it is true that, in a medieval world, just showing up to work at the shit mines constitutes risking death or dismemberment, that sort of thinking isn't in the spirit of the whole XP system. So are we expected to believe that Goodman Bob has, over the course of his (say) twenty-five years of adulthood, faced orcish incursions and giant spiders on average of once every two months or so? And in a pattern that allowed him to escalate neatly through the level ranks? If so, is he the only such commoner, or are there many others? And if there aren't others, what could possibly account for his statistically-awful luck? Finally, if he's regularly engaged in combat, how is he still a Commoner?
The problem comes up most sharply for Commoners, of course, but it arises for the other classes as well. Of all the NPC classes, the only one that can routinely expect to be engaged in combat is the Warrior. Aristocrats aren't going to fight all that often, and Experts and Adepts will want to stay far from the battlefield unless they're there for a specific purpose (and being well-paid for their services). So how can it be that there are so many high-level NPCs with NPC classes running around?
You cannot argue that all NPCs are low-level. For one, the DMG guidelines simply don't support that approach. For another, there is a major problem in the world when every guard, ruler, and shopkeeper are vulnerable to death from even casual player action, let alone from all the horrid monsters that roam loose in the average world. A world in which the players are the only active living things, and everybody else is static, is a world that doesn't make sense. If the players are advancing their craft and skills, then so must the NPCs. People grow and learn things all the time. A world in which people don't is a world that doesn't make sense.
It is unreasonable to assume that NPCs never advance; after all, they clearly do. It is also unreasonable to assume that every NPC who has more than a single level has engaged in large amounts of combat, dungeon delving, or other forms of life-threatening dangerous leisure. The necessary conclusion is that there are other ways than Encounters [tm] to earn XP. But what should these ways be?
Older versions of the game offered bonus XP to each class for accomplishing various tasks and feats. Warrior-types, for example, got bonus XP for defeating an enemy. Rogues got extra XP for disarming traps. Wizards got extra XP for creating magical items (but not for casting spells, because I guess that would be too easy). This idea has some merit.
Unfortunately, it also has some flaws. The most notable flaw is that multiclassing is much more of a "thing" than it used to be. Should a character with one level each of wizard, fighter and rogue get XP for all of the above-mentioned tasks? Why or why not? Not an insurmountable problem, but still, it has to be considered. Likewise, what of a warrior who takes maximum cross-class ranks in Open Lock? Should he get XP for succeeding at an Open Lock check? And if so, should anyone earn a bit of bonus XP every time they successfully damage an opponent in combat?
What about out-of-combat abilities? Things that have no real bearing on adventuring? It seems completely rational to assume that Wayland the epic blacksmith has never seen a day of combat in his life, and has earned his marks entirely through standing in front of his forge for fifty years doing nothing but perfecting the art of making a horseshoe. If you want to master something, do it ten thousand times.
Of course, following this line of thinking to its conclusion takes us right out of the whole class-level system and into White Wolf territory. While that idea has some merit, we're playing Dungeons and Dragons, here, so we don't want to molest the system too much. I've talked before about how NPCs should advance without combat, but that doesn't really do enough. Also, any system that includes NPCs must necessarily be available to players.
In the real world, people pay good money to receive an education. I, myself, am spending close to a hundred thousand dollars to have somebody tell me how to make computers do what I tell them to do. The modern educational tradition has a long and rich history, dating back to the Carolingian empire and the universities at Aachen. Even further if you want to count the Greeks, and who wouldn't want that?
It seems reasonable to conclude that earning XP through education is a thing that humans can do. It is, therefore, also reasonable to assume that it is something that characters can do. It also very neatly answers the question of how the pampered aristocrat boy-king can somehow be level 10: he has spent his entire life being schooled in the arts of combat and courtly ways by the very best tutors money can buy. It explains how the correspondence-course hermit wizard who has never stepped foot outside his tower can have somehow amassed power greater than that of most PCs.
Of course, one still learns by doing, and PCs can certainly earn XP through the old standard ways. However, they, like any NPC, can invest some of their found (or earned) wealth in education.
Tying this to NPCs also helps to neatly explain the gap in wealth between PCs and NPCs. While this is a necessary mechanic from a game-balance perspective, handwaving it by saying that NPCs have spent most of their gold on self-education provides a consistent in-game explanation for both the wealth gap and the fact that there simply aren't that many adventurers in the world.
Characters, PCs and NPCs alike, can exchange gold for XP. The specific mechanics of this are left up to the DM: the expenditure of gold can represent the cost of hiring instructors, procuring rare books and instruction manuals, or losing raw materials to mistakes and missteps. It can also include the cost of healing and de-poisoning due to training mishaps. Whatever the gold is spent on, it is gone, and in exchange the character earns the appropriate amount of XP.
Availability of training is up to the DM. Naturally, a character must have access to the appropriate resources in order to receive instruction. Whether or not those resources are available is a matter of DM fiat; as a rule of thumb, a character needs to have regular access to an NPC who is at least one class level higher than he is in order to receive training. Characters who do not have access to such an NPC double both the time and gold cost of their training; see below.
Characters do not need an instructor in order to train; the great minds of history are remembered because they came up with an idea nobody else ever had, and people teach themselves new techiniques and tricks from scratch all the time. However, characters, like humans, benefit enormously from guided instruction; this is why not having an instructor is so much slower and more expensive.
Exchanging gold for XP as a monetary cost, and also has a time cost, to represent time spent in learning. This time cost is much like the time spent creating a magical item; the more one spends, the longer it takes, and a character must spend entire days at a time learning (though the days spent do not need to be consecutive). At the conclusion of the training period, the character gains the desired amount of XP, which can then immediately be spent to gain a level, or for other purposes.
As in the real world, the more education one receives, the harder it is to learn even more. At the upper echelons of the class structure, a character might be breaking new ground with his research and training. Thus, the higher up in level a character goes, the more his training costs.
Experience is purchased in increments of 100 XP. The amount that each block costs depends on the character's current level, as follows:
|Current Level||Cost for 100 XP|
Thus, a beginning character could achieve level 2 by spending 250g, whereas a 19th-level character would have to spend 142,500 gold to achieve level 20. If the character had no instructor, as is fairly likely at such a high level of play, this cost would be doubled.
Each block of 100XP purchased requires a character to spend five full days in training to earn. These days spent training do not have to be consecutive, but the character must do nothing with those days but train, and he does not earn the experience until the training is complete.
Presented here is a table summarizing the costs in both gold and time for advancing from one level to the next using this process.
|Earned Level||Gold Cost||Time Spent|
Thus, the total cost for advancing from 1 to 20 without going on a single adventure would be 467,250 gold, and would take just over 26 years. This is presuming that an instructor was available through the entire process; if a character was breaking new ground from level 18 onward, the cost would increase to 699,750 and the time spent would be 31 years.
Note that the average wealth by level of a level 20 PC versus a level 20 NPC differs by 540,000. While much of this is due to the fact that players are "creating" a great deal of wealth by returning it to the economy, this curve goes a long way to providing an in-game explanation as to where that vast wealth difference comes from.
This curve, while it will work just fine in an E7 game, is not meant to simulate real-world training times. In the real world, if the supposition that level 4 is the target for a university professor, such training would be available from nothing within 300 days from achieving adulthood.
Of course, a final supposition would be that a person only gains their first level upon reaching adulthood; this "first level," with its maximum skill rank of level + 4, represents all of the little things a character has picked up during their upbringing.
It should be noted that most of this training and cost is technically out of reach for the average NPC with NPC class levels. If a strict interpretation of this discrepancy is desired, it is perhaps acceptable to decrease the training costs for NPC classes by a factor of 10.