I’ve been trying to think of “creative” materials to use in my fantasy world. How do you think bismuth would fair as the base for armor/weapons?
Not well. Bismouth is a brittle metal, and won’t hold up in combat. It was used as component in some bronze alloys but, as a metal, it’s unsuitable for weaponry.
If your setting is using bronze age technology, it’s possible they’d use bismouth contaminated tin and copper, to produce bronze, but unless your character is a smith, that’s not the kind of detail which would be relevant, and trying to wedge it into exposition could be awkward. Even then, it’s more likely that they’d view it as some variant of tin or lead.
So, let’s step back from this and dig into the more general question: How do you go about incorporating “creative materials,” into your setting?
Before you can answer that, you need to answer two previous questions. Why do you want those materials? And, what do you want to do with them?
When you’re creating a setting, introducing fantastical elements can help to make the world more memorable. Your setting has elves, has magic, has vampires, whatever. Over time, the audience will acclimate to certain elements in a genre. So creating a fantasy setting today where almost anyone can perform some basic magic isn’t nearly as memorable as if you were writing the same story in 1930. Within that context, unusual materials can go a long way towards selling that.
At this point, you can sometimes get more attention by eschewing parts of the, “standard fantasy setting.” Which is to say, if you want your fantasy characters fighting with bronze, iron, or steel weapons (depending on the technology they have), you’re not under any obligation to include these things simply to be different. One thing that doesn’t suffer from diminishing returns is creating compelling characters who behave realistically, in a way the audience can identify with. Unusual metals and mystical artifacts are there if they serve your story, or help you build build detail into your world, not because you must include them.
In very simple terms, you can use strange or exotic materials along with other fantastical elements to separate your audience from the world they know. You create a less grounded setting, which affords you greater control over your world. Depending on the kind of story you’re trying to tell, this can be a benefit or a problem.
The second part of this is, what your material does in your setting. There are a few ways this can go.
If you’re inserting a material as a replacement for something that existed historically, then that’s going to build towards your setting’s strangeness. If this sounds like it has to be a 1:1 conversion, that’s not strictly true. Your setting may have some kind of resin, or hard bones that function as a replacement for armor or weapons. You may have some kind of sea creature with a carapace that will hold up for decades after death, and can take a serious beating. You may, simply, have some alternative animals that are used as mounts or pack animals. The important thing is, you’re filling a cultural niche with something that doesn’t exist in the real world.
Replacing elements will lead to a less grounded, more fanciful setting, particularly as you stack up elements. Juggling elements like this can make your setting more complex and memorable, or it can render the entire thing obtuse, and difficult to understand. Handling these kinds of elements becomes a juggling act. Said juggling act becomes more difficult when you try to write to people who are familiar with the genre and newcomers. There are real rewards for this kind of approach, and it is something I’d recommend you experiment with or at least research, but it’s not something you can expect to nail on your first attempt.
You can introduce elements that replace anachronistic concepts that wouldn’t exist in your setting, but would be familiar to a modern audience. The idea of a fantasy setting with cell phones may strike you as odd, but there are plenty of settings that do incorporate modern technology into a fantasy setting under the guise of something else. Communication crystals or spells allowing telepathic contact and remote viewing.
The tricky part here is figuring out exactly what all of these pieces would reasonably do to your world. Even minor tweaks can start to have significant consequences. More aggressive wildlife will mean better fortified settlements. Without that, the settlements would be overrun and wiped out. So, this becomes a necessary precaution. If you have truly massive pack animals, then major trade routs could easily form along land routes instead of along waterways, leading to a very different geography, potentially one with far less interest in water travel in general. This is particularly true if you have vitally important materials that don’t naturally occur near the water.
Conversely, if your fantasy setting is dependent on something pulled from the water, they may go even further. Magical research, and even mundane technology could go far further towards deep sea diving if some leviathan down there is the source for carapace armor, or the only place to mine some otherwise unobtainable ore.
However strange your world becomes, it’s vitally important to remember one thing: For your characters, this is normal. (Unless they’re native to a different setting and get dumped into it. At which point, everyone around them will still be in the mindset of, “no, this is normal; stop gawking at the sledge, they get nervous when you stare at their eyestalks.”)
If you’re not chasing strangeness, then unusual materials often become a way to indicate that a given weapon or item is special in some way. The first example that may come to mind is Mithril, from Tolkien, but there’s actually a long history of people making up metals and imbuing them with special properties. Some quick examples include: orichalcum, which Plato ascribed to Atlantis, and adamant (which is where we get the terms adamantium and adamantite), which referred to an improbably strong metal or substance (and is the root for “adamant,” in modern English, if I remember correctly).
Unusual materials also have some basis in history. (Not counting orichalcum, which may have been an actual alloy, or could have been something Plato invented for rhetorical effect.) Superalloys like crucible steel and Damascus steel were quite real. Similarly meteoric iron was sought after because of how valuable the metal was to a smith. Chemically most of it is an iron/nickle alloy, but this stuff was one of the first sources of metallic iron, before smelting technology was developed.
If your setting has unusually advanced magic, it’s possible they’d have access to metals that just wouldn’t exist historically: like titanium. In the real world, titanium wasn’t discovered until the eighteenth century, and wasn’t refined into a metal until 1910. (Somewhat obviously, the minerals were always there, but they went undiscovered until 1791.) However, if your setting has magical means to locate and identify metals, and access to forge temperatures far beyond what real world technology allowed (specifically, high pressure, non-carbon based forges, for titanium), it’s possible you could have this stuff in your setting. (At that point it’s probably worth remembering that Titanium was, explicitly named after the Greek titans, so the name may not carry across, even if the metal does.)
Mixed with all of this is the idea to single out a weapon and indicate it’s special. This has some historical basis. Weapons made from superaloys or meteoric iron were highly regarded historically, and may be the origin of stories about magical weapons and artifacts. It’s entirely possible your otherwise grounded setting may have a sword made from starsteel, that’s a symbol of the king, or a “magical” sword with the wavy bands of Damascus steel. This stuff was real, and for users who were unfamiliar with the origins, Clarke’s Third Law holds. (“Any sufficiently advanced technology is indistinguishable from magic.”)
Somewhat obviously, there’s nothing to stop you from having an artifact made from some material that’s been otherwise lost. This is, sort of, how Plato used Orichalcum in his discussion on Atlantis. The material and objects created from it were almost forgotten, but (supposedly) still existed.
It’s entirely reasonable that your character may be questing for an onyx-jade sword, or something equally bizarre, in an otherwise grounded setting. This works particularly well if your setting has a pattern of fallen civilizations, and exists in a dark age after some lost golden era. (Incidentally, this fits with how Europe viewed itself through most of the middle ages, ending near the enlightenment. So, there is historical precedent in this approach.) This can also leak over into outright science fiction elements, if that’s what you want.
The most important part of incorporating “creative materials” into your setting is in the name, be creative. Look for opportunities where you can start to seriously alter your world. Ask yourself, “what would this mean to the civilizations of my world?” Look for opportunities to connect your ideas, and how they would interact with one another. But, most importantly, be creative. If you want to have something fanciful or strange, don’t feel limited to the periodic table.