Githyanki cultural nuances
Most of these come from BoGr (credit to Azure for many of them), though I've made up a few for this article.
Introducing a weapon to someone: Between two githyanki, this is often a gesture of friendship and trust. One githyanki unsheathes the weapon (if necessary), mentions its name, and describes something that makes it interesting or unique. This can be anything from "this is the blade worn by members of my Order" to "this blade has slain over a hundred ghaik" to "this weapon slew the hated and infamous zerth so-and-so" to "this is the blade of (previous owner, who had certain admirable qualities)..." The second githyanki usually either thanks the first for the introduction and/or compliments the weapon, the owner, or refers to whatever story the first githyanki provided about the weapon.
In the case of a few especially unique and sacred blades, it may be frowned upon to resheathe such blades without putting them to use. The wielder will either refrain from unsheathing the blade during the introduction, or deliberately nick themselves with the blade after drawing it. (Of course, a githyanki may also stab a graith just to keep the tradition going.)
A githyanki may introduce her weapon to a barbarian as a gesture of respect, but this is rare, for it is a rare barbarian who is worthy of respect! More often, if a githyanki introduces a weapon to a barbarian, it is as a threat or a warning. Example: "This sword pointed at your stomach is named Anguish, the blade of Araz'kaa'leth of Hematite, and it has been the bane of over a thousand barbarians!" A githyanki may also introduce their weapon this way to a mind flayer, githzerai, or githyanki renegade.
If the weapon is an "heirloom" passed down or acquired from someone the githyanki respected or admired, it may be drawn as a reminder of some quality of the previous owner. For example, a githyanki commander might introduce the weapon of "Ragak-Tul of the Band of Lapis, called the Fearless," while exhorting his troops before a battle.
Insulting another's weapon: This is a great way to pick a fight with a githyanki, if you're determined to do so. It is not very common for githyanki to do this to each other, but they frequently do it to barbarians, githzerai, and so on. If the blade is special in some way -- such as a silver sword, the weapon of any knight, the weapon of an Order, the heirloom weapon of some famous githyanki -- then insulting a weapon may be construed not only as an insult to that githyanki's personal honor but also that of the knighthood, the Order, the famous githyanki hero, and so on. Additionally, since a fair number of githyanki sexual euphemisms and slang refer to weaponry, the possibility for double-entendres exists. (A fact which many githyanki playwrights have used to their advantage.)
It's acceptable for one githyanki to point out that another's crossbow string is frayed, or that their sword could use a session with a whetstone. However, they phrase such comments carefully to avoid giving offense (or amusement).
Use of the term "to *know*:" Githyanki do not say that they *know* something in the way that the githzerai Dak'kon in PS: Torment did. Generally, they only use the term in the context of psionics. If a githyanki *knows* your mind, it means she used detect thoughts on you, or at least had a telepathic conversation with you. If she *knows* fire, she's a pyrokinetic. Using "to *know*" in the Dak'kon fashion is regarded as highly githzerai-like.
Keeping weapons nearby: Githyanki almost never go unarmed anywhere. Generally, asking another githyanki to go unarmed is a considerable insult to one's honor. A githyanki will often sleep with a blade either beside him or within easy reach of the bed. While a githyanki may not always carry around all her personal weapons at one time (especially since some warriors literally own dozens of weapons), they will always have at least one weapon around -- and usually many more.
Bowing: This depends on a lot of factors. If the githyanki involved are from one of the more ancient cities or belong to warbands or Orders that are more traditional when it comes to formal etiquette, you're more likely to see the gesture. If the difference in rank between the githyanki involved is substantial, or if both githyanki are of high rank/status, the same applies. Exactly how one bows depends on the ranks of the githyanki involved, and a generic "I'm not sure what your rank is" version exists. Depending on context, a bow can even be used as an elaborate or subtle insult. Some parts of the Githyanki empire are much more lackadaisical about bowing than others.
Kneeling: This is rare in githyanki culture, as it has cultural associations with thralldom and decerebration. However, one would be expected to kneel in the presence of the Revered Queen or other members of the royal family. A githyanki might also kneel when making a contrite apology, when making an impassioned declaration or oath, during certain religious ceremonies, or (rarely) when an extremely sacred weapon is formally introduced. Githyanki never kneel before barbarian leaders, and would consider it sacreligious to do so.
Holding a weapon by its blade: This is an offer to parley, and an offer of alliance. To a barbarian, it can mean the githyanki will refrain from stabbing you... for now.
"Brother/sister" vs "cousin": Adult githyanki often refer to each other as "brother" or "sister." While it is common to refer to a duthka'gith as "cousin," it's much more friendly to refer to one as brother or sister. A gith pirate or Athasian gith (who is considered worthy of respect) might be called "cousin" as well. A githyanki who calls a githzerai "cousin" is likely to be either a Reconcilist or maybe a Unifist, though it's moderately socially acceptable for other githyanki to use the word "cousin" if they preface it with an insult: "our wayward cousins," "heretical cousin," "not-cousin," etc.
Exclamations: A githyanki may refer to either Gith or Vlaakith this way. Some example oaths: "By the Liberator!" "Gith's blood! "Revered Queen!" "Thank the Liberator!" etc.
I really like this. Nice work.
"La la la, I'm a girl, I'm a pretty little girl!"
--Bel the Pit Fiend, Lord of the First (in a quiet hour of privacy)