Note: I am discussing that topic from my own point of view, like I underline it below, trans people are very diverse, so naturally different trans people may feel differently about trans representation, if you have trans people at your table, listen to them first.
The other day someone said they wanted to include trans non player characters in their game but did not know how to show or communicate that they are trans. I thought about it and here are some of my thoughts as a trans person.
I would say that:
A) You can include trans characters without the need to show that they are trans. Being trans can be a private thing for some NPCs. If you do that it is important to not treat their transness as a dark secret or as a dramatic reveal, if a PC get close to that NPC try to make the reveal casual.
B) You can simply state that a NPC is trans when you introduce them. You can say "you enter into the bakery shop and the baker, a cheerful trans woman with brown hairs and a warm smile, great you".
I like that B offer clear representation and normalize trans people in a casual way. It can be a bit meta but I think that clear communication and representation are worth it.
This is worth a thought: when you describe cis people you simply state their gender, you don’t try to remain immersive by communicating their cisness and gender only through physical descriptions. If saying "you see a young woman with brown hairs, wearing a blue dress" is fine, casually saying "you see a trans woman with brown hairs, wearing a blue dress" should also be fine.
When presenting a NPC as trans you are not saying that their transness is automatically apparent, you are simply informing the players that the NPC is trans, you are not necessarily communicating this to the characters. I would let a player choose if their character notice that the PNJ is trans or not. People perceive us in different ways, how we are perceived is not a fixed trait. (Please, don't ask for perception tests to notice if a character is trans or not, this put emphasis on "passing" and is kind of transphobic.)
If you decide to physically describe a trans character don't present some of their physical traits as "non passing" or as being noticeably odd for their gender. Don't put the focus on how a trans person pass or not pass. You can frame some trans traits in a positive light but be careful not to base your entire description around them, also include traits that are not related to being trans. Exp: "You see a tall trans woman with dark hair and beautiful broad shoulders, she is wearing a..."
This is mostly for binary trans characters, but with some nuances, the same can be applied for presenting and describing non binary characters. The main difference is that you will introduce them using non binary pronouns and often their occupation. Exp.: "You see a knight, they look brash and are wearing a fine set of armor." I would also be ok with adding "they are non binary".
Other things to consider when creating or roleplaying a trans character:
Don't forget that trans people have very diverse backgrounds and life stories. Try to give them diverse cultural backgrounds, educations, careers, ages, loyalties, attitudes, personalities and gender expressions. Their path toward self discovery, coming out and transition are very diverse too. Note that trans people may also remain in the closet or avoid transition for very diverse reasons too. Try to include more than one trans NPC to also represent trans people diversity. Like you can have old butch trans woman warrior and a young closeted non binary scholar.
Family can be a big thing for trans people, their family can be a source of anxiety or support. Again, there is a large variety of experiences: some trans people may have cut all ties with their families, some may be in conflict with them while some other may receive a lot of support. I think it is important again to show different interactions for different trans people and different family member. A father can be very unaccepting while a uncle can be very supportive. I would say try more often to show family members as distant or supportive to avoid creating overemphasis on rejection. Don't ignore family conflicts but don't make them the norm too as it can get tiresome to see trans character always struggling with their family.
Trans people don't exist in vacuum, they have friends and allies that support them. Try to give them some close friends or allies, people that support them or that simply appreciate them. These friendships may have started before or after their transition. Often trans people have a wide variety of friends of diverse genders, coming from the different parts of their life. On the other hand some trans people may experience a lot of isolation, which can be a source of distress for them, again don't make this the norm but it can be something to explore.
Trans people, like everyone else, may be single or have a partner (or more) and have diverse intimate relationships. Some may be in a relationship with a cis person, some may have a trans partner, some may be strait, gay, poly, ace, etc. Again the keyword here is diversity. Don't forget that your cis NPCs could also have a trans partner.
Skills and past careers
Depending of their background, trans people may have acquired a wide variety of skills, especially those who transitioned later in life and went through different careers. In a fantasy setting some trans people may have experienced a drastic career change due to the gender roles of their society or culture. But then again, trans people are good at challenging gender roles so there is no fixed rules here. You can have a trans woman baker who was a soldier before or a trans man who remain a well know healer and "midwife".
Networking and community
Trans people network together to learn about themselves and how to transition, also to help and support each others. This is especially true with internet but you could easily imagine a fantasy trans network about helping each other finding hormones potions or more mundane resources. Give your trans NPCs other trans allies, friends and contacts. Make trans people interact and discuss together, make them part of a community. Again, also consider that some trans people can be isolated and cut away from that networking, which can make their transition harder or be a source of distress.
Ups and Downs
Trans people often have both a mix of low and high self confidence, sometime they can be very self confident and self affirming while other times they can experience a lot of anxiety and self doubts. This is often part of the trans experience, sometime you feel super courageous and defiant but other days you may feel super insecure about your appearance or something else about yourself. Some trans people also experience up and downs with their gender dysphoria, sometime they can feel super dysphoric, other time they forget about gender or are gender euphoric. (Note that not all trans people experience gender dysphoria, some trans people simply feel more comfortable in their chosen gender).
For your trans characters who choose to transition, don't forget that there is different ways to transition, someone can do a social transition (changing name and pronouns) while others can take hormones to also transition their body. Depending of your setting there may be different ways to transition socially or physically. Modern days offer different options (name change, hormones, surgery, etc) but you can also easily imagine ways to transition in other settings, like a renaming ritual or spell, hormones potions, magical pools, etc. Try to combine these with other services or social functions, like that trans clinic could also be a good bioware clinic and that hormones potions witch could also be a wonderful healer.
Somethings to maybe consider about magical or high tech transitions: is a "perfect" transition possible? Or is it a long and difficult process? Do it require frequent uses of magic or injections that reflect how modern trans people have to regularly take hormones? How accessible transition is? Is there different ways to transition that have different costs or benefits?
Trans people can face discrimination, this can be something that you explore in play but be careful if you choose to do so, even if it only affect NPCs, take the time to discuss with your players to see with what they are comfortable with or not. Also be careful not to define trans character only through the discrimination they face. If every trans characters are show as facing discrimination and suffering this teach to trans people that we can only experience our transness through suffering and struggles. This is why you need to be careful to avoid making discrimination the norm or default, even if discrimination can be a common thing, use it sparingly at the table or in your writing and don't be afraid to imagine trans characters who are well supported or settings with no discrimination at all.
Some tropes to avoid
- Trans identity as a dark or mysterious secret.
- Dramatic outing of a trans character.
- Trans people who don't reveal their identity to their partner.
- Pre transition life coming back to haunt trans characters.
- Blackmailing trans characters with the menace of outing them or revealing their past identity.
- Murdering trans people or suicide.
- Assassins, spies or monsters who switch sex as a weapon.