Wednesday, January 31, 2007

NPC Creatures Populations

Monster NPC creatures in MMORPGs are typically statically located, and respawn out of thin air, for the camper's greater delight. What is rarely considered is that perhaps it would be possible to have a realistic monster population in a MMORPG.

Realistic monsters, be they rabbits, goblins or dragons, would have purposes on their own. Rabbits need to survive, and to do that, they only
need to eat, avoid predators and reproduce. If the rabbit population goes up too much, however, food starts getting scarce, and the rabbits get more daring; they go eat near potential predators, namely human settlements. What happens then? You get a good old-fashioned quest. Farmers, or authorities who have been contacted by them, will pay adventurers, typically very meagerly, to take out some of the rabbits that are ravaging their vegetable crops. For rangers, this is good news, since it means they get something extra for hunting rabbits - plus, the rabbits are plentiful.

Another thing that might happen if the rabbit population goes up is that other predators will become more plentiful as well. Big bad wolves, who require fresh meat to live, will become more common, and while they don't typically attack humans, they can be a problem to livestock and hapless travellers. The result? More questing. Wolves tend to defend themselves better than rabbits, but they also have better furs, and more meat, for those who aren't afraid of uncommon food sources. No lucky rabbit foot, though.

So right here and now, we have an equilibrium. Rabbits can't get too common without encouraging wolf population growth, which need rabbits to live, otherwise their population will go back down; and if it doesn't, a hundred adventurers are ready to reason with them and make them see the errors of their way, usually in a rather permanent way.

Now, having balanced populations isn't everything, monsters need to come from somewhere. For rabbits, this is not too difficult; you add a hole in the ground, call it a burrow and make rabbits pop out of it; if you want extra fancies, you can have rabbits hide back in it when they sense danger. In this way, the rabbit population can never go lower than the number of rabbits left in the burrow. Rabbits will always exist.

When it comes to wolves, however, things might be different. While wolves will typically lodge within caves and other natural nice places, those locations are rarely inaccessible to adventurers, who can go in and try to fight the whole wolf pack; if they succeed, they have one less pack of wolves to care about. However, if too many adventurers hunt wolves, they might become scarce, and unless some lawmaker is ready to take some time away from destroying demons to declare them an endangered species, you might see the total destruction of all wolves within a certain area. Wolves can migrate from other parts, but for a while, rabbits might become a problem.

Now, most animals are easy to understand, but when sentient creatures are involved, things get more complicated. Goblins usually have their own agenda, and when they are not solely preoccupied with survival, they will start to get organized. If they are evil little goblins, they will raid settlements in hope of finding sustenance in the form of rations, or perhaps loot, to quell their hunger for shininess. If that happens, then you have goblins with actual loot; goblins that adventurers will want to kill; and goblins which will fight back much more fiercely, since they are both large enough to have raided in the first place, and made stronger from the weapons, armors and trinkets they acquired; we are to presume goblins cannot make such things on their own. Goblins which aren't technically evil might simply decide to defend themselves against invaders, in which case it is the players' role to play the evil part and exterminate helpless populations.

This presents a lot of story opportunities. Adventurers can venture in the goblin outlands and raid some villages. They can do so to protect their homelands, or simply because they like killing goblins. Similarly, if they go after goblins who pillaged a town, they might want to keep all this nice loot for themselves, or give it back to their rightful owners. But adventurers can also venture further in, and try to exterminate bigger goblin populations; and that causes dilemmas. Is it alright to kill young goblins, knowing they would most likely become raiders? The game doesn't offer the answer, it only presents the question. Players make their own stories, and set their own rules.

What about creatures which aren't technically part of populations? Dragons are rarely seen in groups, since they usually don't mingle very well. If a dragon enters an area, it will have to not only claim it for itself, but also exterminate would-be predators, acquire their shinies and find reliable sources of food. They also offer a much stronger challenge to adventurers, and typically a larger loot as well. Since they work alone, or in small groups (For example, a dragon, its mate and its youngs), defeating a dragon leaves the area unoccupied. Migrating creatures may want to seize the land, or perhaps retake it if the dragon took it from them in the first place. Dragons themselves have to come from somewhere. If you don't want your dragon population being exterminated by the players, that location must be either inaccessible to the players, or so suicidal a place that even large raids of seasoned adventurers could not hope to last long in such a location. In either case, you simply control the dragon population by having extra dragons migrate out of the place and seize a suitable lair, possibly away from another dragon (If your players are too lazy to do the dragon-slaying themselves).

With different creatures come different rules, and if you change one's rules, it might affect another's; this is called holism, which basically means that changing one part of a system, particularly one in equilibrium, might change other parts of the system. For more information on holistic MMORPG development, I recommend checking the lengthy but interesting read at

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