1. Not thinking about basic infrastructure.
How do they eat? What do they eat? Who takes away the garbage? Who deals with their bodily wastes? How do they get around? What do the majority of people do to survive? You're not just constructing a society, you're creating an economy. People don't oppress each other for fun — usually, systems of hierarchy and oppression have an economic component to them. Maybe you need a lot of peasants to grow labor-intensive crops, or maybe you need lots of cannon fodder in your space war. Maybe your only source of protein is a weird fungus that needs to be tended by specially trained people. Maybe everybody's eating algae. In any case, there's nothing worse than a fictional world where there are elaborate social structures, which seem completely separated from the realities of food, shelter and clothing.
For example, even in societies where elites are allowed to kill their slaves freely, most of the elites will not do so just for fun, a society where most people are slaves and every elite kills their slaves for fun is doomed to economically collapse in one or two decades, not to mention that it is against human nature to kill or harm others for fun. Elites oppress slaves, serfs, commoners, etc. because of practical reasons(i.e. their vested interests or the need to uphold the tradition or the official ideology), not because they like it or anything else.
Laws that ignoring basic human needs will be broken by the vast majority of people on a regular basis. For example, in communist countries, a major result of banning trades and the existence of "market" is a thriving underground economy where almost everyone sells and buys something to the black market to support themselves and their families.
Even you work on a world during a war, a great disaster, etc. it is still necessary to depict the daily life of the people, and in these cases, you must think how the war, the disaster, etc. has changed daily life.
2. Not explaining why events are happening now.
Chances are your story revolves around all heck breaking loose in your fictional world. (Or your fictionalized version of the "real" world.) One major worldbuilding flaw is not explaining why heck is breaking loose now, as opposed to 20 years ago or 20 years from now. Why is the dark elf army showing up now? Was there something preventing them from showing up, which has been removed? Will it be too late if they wait another year or two? Often, if your plot is swinging into motion for reasons that feel purely arbitrary, that's actually a failure of worldbuilding. You haven't fully accounted for the things that kept your villain in check, and probably also for the factors that keep other political actors in your society in check as well. And that's a larger issue — every society has checks and balances. Even an absolute monarchy has invisible lines the monarch can't cross. Sometimes you can't figure out how these checks and balances worked in a particular era, without reaching beyond the official history as sanctioned by the people in charge.
On a related note, if you're drawing on real-life history, for your fantasy world or your future history, don't just read works by historians from the dominant culture, or works focusing on the ruling class. Historians have done amazing work on discovering what ordinary people and marginalized groups were doing during a lot of eras, and there's plenty of resources on what was going on in, say, the Middle Ages outside of Western Europe. To the extent that you rely on actual history in your world-building, you should reach beyond the Kings and nobles of a few Western countries. Image by Frederic St-Arnaud/CG Society.
Even your in-world people don't know why things happen, it is still necessary to have explanations for every event in the world.
3) Creating fictional versions of real-life human ethnic groups, that never go beyond one dimension
This is a huge problem that tons of creators seem to struggle with. But as a rule of thumb, if you want to have Belgians in your novel, you're going to have to try and create an accurate view of Belgian society. If you decide that instead of Belgians, you're going to have an alien species called the Bzlgizns — who are basically Belgians except they've got antlers — you still have to try and make them well-rounded and as nuanced as possible. Ditto if you're creating a secondary world where there happens to be a land of magical creatures called The Belge, who are still basically Belgians. Really, you should make sure that any cultural or ethnic group you create has multiple dimensions and a sense that its members have their own subjectivity, and a believable culture. Whether it's the culture that your main characters come from, or a culture that they see as the "other." But it's also a really good rule of thumb that the more your fictional group resembles real-life Belgians, the more you ought to worry about being true to life. Changing "Belgians" to "Bzlgizns" doesn’t actually let you off the hook for presenting a true-to-life portrait of people from Belgium.
4) Creating monolithic social, political, cultural and religious groups.
Everybody in a particular ethnic group agrees about everything. Every member of the ruling class, or the working class, agrees about everything. Every citizen of a particular nation holds exactly the same set of opinions. There is one version of history that absolutely everybody agrees on. Every member of a religion interprets the tenets of that religion in exactly the same way. That sounds plausible, right? Maybe if you've never been around actual humans. In real life, if you get three members of a particular in-group together, you'll probably hear four different opinions on most of the group's major concerns. Asserting that all Christians agree on all matters of doctrine is probably a good way to get laughed out of the room. So when you imagine the ruling class of your world, it's safe to assume that no two members of it will agree on much — and when you retell your fictional history, remember that nobody's likely to agree on what actually happened.
For another example, if you have a elitist country that has an elite caste consisting of about 200,000 people, and the government is fighting against a big uprising from the commoners, there are always some members of the elites joining the uprising side no matter how united the elites are to each other, it is just totally impossible for every member of the elites to fight and die for the government considering the total number of the elites.
In other words, either your conpeoples are humans or your non-human conpeoples will very likely to possess some nature similar to that of humans. Alien sentient species who are totally dissimilar to human beings are very hard, if even possible, to depict. Therefore what happens to real human societies will also happen to your conpeoples, and you should never forget that. Full stop.
5) Inventing a history that is totally logical
n an imaginary world, the strongest side always wins and the people who are in charge are always the descendants of the people who were in charge 100 years ago. But real life isn't like that — history is full of odd quirks and happenstances, and powerful people often make huge miscalculations that wind up costing them dearly. Just think about weird happenstances like Ireland being divided in half. Or Korea. Or Germany, for nearly five decades. Why is WashingtonDC the capital of the United States instead of Philadelphia? Why did the Portuguese have their own colony in India until 1961? History is weird. And things that seem inevitable in retrospect usually seemed anything but at the time. So a totally logical history will never pass the "smell" test. And speaking of smell...
While history does not always make sense, it does not mean one can do whatever they want. Some basic senses should exist. Considering 2), all seemingly nonsenses must have extraordinary but still in-world sensible explanations.
For example, look at this map:
Hux Kham will always have a sizable standing army and probably a conscription system, even its army regularly involves in politics(like causing coup d'etats), the people has a strong pacifist culture, and the country has a good relationship with all its neighbours. This is Hux Kham is a landlocked and relatively small country between larger countries like Qonklaks, Naria and Yerlan, therefore, politicians and most people in Hux Kham will support the existence of military forces.
For another example, look at this map:
If Lake Khuda was an origin of agriculture and a kind of writing system, then ethnicities of surrounding areas would have adpoted writing systems early on, for example, all major ethnic groups in Ebo Nganagam would have a long tradition of writing down their own languages regardless of their initial attitudes towards writing.
6) Not really giving a strong sense of place, like what it smells like after it's been raining.
You can spend hours and hours thinking about the history and culture and mores of your imaginary land, and how people interact and the ways that different religious and ethnic groups collide. But if you don't make me feel the dirt under my fingernails, then you still haven't created a real place. If the reader doesn't get a little lightheaded from the stench of the polluted river, or transported by the beauty of the geometric flower gardens, then something is missing. Most of all, there should be a few spots — bars, taverns, crypts, spaceports — where the reader really feels "at home," as if you could imagine hanging out there for real. The purpose of worldbuilding isn't just to do a cool exercise, but to give a sense of place — and all of your thought experiments absolutely have to result in something vivid and alive.
7) Introducing some superpower, like magic or insane tech, without fully accounting for how it would change society.
If your pitch is, "It's just like our world, except everybody can turn invisible at will," then you've already failed. Because if everybody could turn invisible at will, it wouldn't be anything like our world. Especially if this power had been around for more than a few months. Whether you're creating an alternate history or a secondary world or a far future, any technology or power you introduce is going to have far-reaching effects — not just first-order effects, but second- and third-order effects, too. Going with the "invisibility" example, you'd have people using it to spy on each other — but you'd also have a huge boom in heat sensors. We'd start redefining the whole concept of privacy, and pop culture would be massively transformed. There would be whole art forms based around invisible performers, and it might be legal to shoot an invisible intruder on sight (on smell?). You could be here for hours imagining all the ways that the universal power of invisibility would change the world, and you'd probably still just be scratching the surface.
For example, if you have technologies or powers that create a human society with gender imbalance where there are much more females than males, female dominance in these societies will become very likely. Considering 5), it is still possible that males still dominant in a society where most of its members people are females, but in such societies, male dominance will need extraordinary but still in-world sensible explanations.
Some add-ons:
8) Making a society that nearly 100% satisfies your fantasies, hates or fears, be it something based on your sexual fantasy, your fetish, your political ideology, an utopia(your dreamland), a dystopia(the society that you dislike the most), or anything else.
All societies that work, including all of your own con-societies, have goods and bads, fantasies, hates and fears are either too good or too bad considering how the real world works. While your own fantasies, hates or fears can be a good start for worldbuilding, trying to make a society exactly or mostly based on your own fantasies, hates or fears will always make you lost and end up making your own world no more than a pile of nonsenses.
For example, making a society where every male has tons of beautiful girls(all societies that can work have old women and some guys that are unpopular among girls), or making a society of immortal mermaids(except for organisms with a simple body plan, like jellyfish, aging and death will always be a part of life, that is, all sentient beings are subject of aging and death as sentient beings would require a rather complex body plan) in a rather realistic setting will surely make your world tons of nonsenses.
Some more add-ons, they are not just deadly sins for worldbuilding, but deadly sins for anyone who wants to do something:
9) Being stubborn with your own thoughts
This is the most basic of everything. Even it is your own conworld, you must listen to others’ criticisms and ask people constantly(but don’t ask the answered questions again) about everything if you want to make a serious and sensible conworld.
For example, in a realistic worldbuilding project, if you have a small island country that you love a lot, and you want it to have a Japan-like culture and a strong economy, and people tell you that your country should not have a strong economy because it contrays to the general plan for the project, you should not insisting to have a strong economy for it no matter how much you love it.
This has happened in the collaboration of Sahar, the ConWorkShop planet, someone with a country called KMA wants to make it a Japan-like country with a strong economy, while a developing country-level economy and a polynesian-like culture fits it more, and the owner of it does not want to change even everyone else wants the owner of KMA to lower the GDP per capita of KMA significantly.
10) Being uncooperative or trying to vandalize in a collaborative project
Even you don't agree with your co-workers(by co-worker here I mean anyone who collaborates with you to create a world), or even have a beef with them, you have no rights to reject their ideas when their ideas are accepted as a consensus, not to mention that you throw a tantrum, going off on them or even trying to vandalize the whole collaborative project and spreading rumors about your co-workers. Throwing a tantrum or going off on your co-workers or even trying to vandalize the whole project and spreading rumors about them because you don't agree with someone is wrong and there's no excuse for causing such a toxic and nasty drama.
If you do so, no matter what reasons you have, you are toxic and should be judged by the drama caused by yourself, and people will have the rights to be mad at you, to make fun of you and to tell a third party about you and the drama, because causing a toxic drama shows that you have a major personality flaw that most people don't have.
This has happened in Sahar collaboration and caused a very toxic and nasty drama during late 2017 and 2018, you might ask its main participants about the details of the drama in Sahar collaboration.
Also, while people can often mistake Sahar as a project of an insular community with toxic participants, it is just a very rule-based and realistic collaborative worldbuilding project, in short, Sahar is nothing more than a no-nonsense project. If you want to join a project and can't comply with the rules completely, Sahar or other project alike, you deserve to get banned or ridiculed by its participants.
In short, always interact with others with your common sense, if you don't have common sense, learn it. Full stop.
Most of the contents above are taken from https://io9.gizmodo.com/7-deadly-sins-o ... -998817537 , with some examples and add-ons added.
