To use the maiming rules as an example, I wanted to indicate to the party early on that losing limbs was a possibility because I didn't want to blindside them. Not every game allows for going blind or having your arm cut off, so it seemed fair to me to illustrate that it was on the table at the start of the campaign. This is one of the reasons I introduced the NPC One-Armed Fiery Demon.
One-Armed Fiery Demon served a number of functions. I was careful to avoid doing the GMPC thing, but in light of a recent blog post by Tommy Brownell I realized I had been missing out by not having strong and present NPCs in the game that could take a more active roll in the overall campaign. So I introduced One-Armed Fiery Demon telegraph the following things:
|Min becomes One-Armed Fiery Demon|
in the single stroke of a blade
2) People more powerful than you exist in the setting and if you don't respect that power, you can die: One of the first things One-Armed Fiery Demon did when the party met her was decapitate a group of eight Mystic Sword Sect disciples in one swoop of her blade. The purpose of this wasn't to have them watch my cool NPC do something the players can't do (we've all probably had a GM lord optimized or broken NPCs over us and that is never fun). The point here was to show that there are people way more powerful than them in the setting and that they can kill you in an instant if you are not careful.
3) Grudges are a thing in the setting and if you anger the wrong person, it may come back to haunt you or your sect: One-Armed Fiery Demon wasn't just randomly killing people, she had a grudge with the Mystic Sword Sect. This was important because the game has grudge tables and grudge encounters happen. The more grudges players acquire, the more they get stuck in an endless cycle of bloodshed. I wanted them to realize this kind of stuff can affect them.
As the campaign progresses the party has had more and more interactions with One-Armed Fiery Demon and she even became the informal Sifu of Zhi Zhu (a PC in the campaign). They've learned her real name is Min and that ten years ago Lady White Blade of Mystic Sword sect cut off her arm and killed her husband. So she has also been useful giving some background to the setting as well. But she isn't the only character or event I used to telegraph consequences. There are others who have been used to demonstrate what is at risk in the game.
The reason I think this is useful is because so many GMs have different styles when it comes to what consequences are on the table and so many games are different. Not every GM kills PCs for example. I am not particularly harsh, but I also do take a bit of a 'let the dice fall where they may' approach, while trying to be fair and open in the process.