Thanks, that was pretty informative.
Um, I suppose information about Dresdenverse Fae would be pretty useful. It seems pretty inevitable that we'd be quite curious about each other IC.
Okay, well. First, unlike the True Fae of WoD-verse, the Fairies/Fae of the Dresden-verse are not all bosses. It would be as if, to compare them and get a grip on things, all Goblins were also (Lesser) True Fae.
To get to the start, Fairies are magical beings that live in the Nevernever, which is somewhat like the Hedge, though different and not quite as theme-locked. A series of interconnected realms, haunted and controlled and patrolled by Fairies. There are as many kinds, almost, as there are of goblins, and similar to goblins and the True Fae/Changeling, they are drawn from various interpretations of mythology, so a goblin based on the myth of a Kelpie and a Kelpie (Dresden) meeting could be interesting.
As different as they can be, ranging the gamut from small to huge, from very weak to 'stronger than any individual True Fae'*, they follow certain rules.
First, they cannot give anything away for free, or find it deeply against who they are, and so they are natural dealmakers. They love gathering information, as a rule (those that aren't stupid, that is). They are weak against Cold Iron, which unlike the True Fae includes all steel, even mass-produced steel. Which means they're actually fantastically vulnerable, honestly. They cannot lie outright, and they cannot break the word (the letter, of course, can be broken however one wills) or their promises. That's how binding on them. Asking them something three times or making them promise something thrice is even more binding, so they can't even wiggle out of it with a half-truth, or intentionally not trying as hard for the promise, or anything else.
Fairies are divided into three general groups. Winter Court, led by three figures...
The Winter Lady, the Queen Who Is To Come.
The Winter Queen, the Queen Who Is.
And Mother Winter, the Queen Who Was.
Each has different powers and responsibilities, and different abilities to interfere in the world. The Winter Lady interferes with mortals all the time, the Winter Queen sometimes, and Mother Winter, vastly more powerful than both of them combined, almost never.
In fact, Mab is unable to affect people who aren't in some way tied up/related to something she is doing. Bound by pledge or oath or war or something else. Hence, the Winter Court has a single mortal, the Winter Knight, who received the Mantle of Winter, and all of the powers with it.
Winter Court rules half the year, at the height of their power in the height of Winter, at their wane just before they switch over, and they are known/seen as cruel, monsterous, and dangerous.
Summer, on the other hand, can be quite brutal as well, but Queen Titania and the current Summer Lady, wise and beautiful Aurora, are definitely viewed in a better light.
Most Fairies though, are Wyldfae, somewhere in between, though in times of war between Summer and Winter, they are forced to pick sides.
The Erlking is the King of Goblins, and runs the Wild Hunt, and is also the Summer King. To clarify something really complicated, the King rules anything he has independently of the Queen system, and is stated to have an "opposite nature" from his Season's Queen. So whereas Titania is one via of Summer, he is the 'I'm leading a hunt to murder people isn't it great' view of Summer.
Just like the Winter King, Santa Clause, is the Hearth and Fire and Chestnut version of Winter (while also being a dangerous badass).
Okay, that rambled some, but, tldr: They can't break their oaths, they come in many forms, anything with iron in it hurts them, they have a Summer and Winter Court ruled by three Queens each, who take turns sharing power based on the seasons.
*Such as the Eldest Gruff, quite probably, Leansidhe, MAYBE a Lady but possibly not actually, and Mab and Titania and the Erlking and Santa Clause, less uncertainly. Note, Mab is not even close to strong enough personally, or honestly even with all of the armies she has (even if she literally emptied the border with the Outsiders), to conquer Arcadia, but no, there's not a single member of the Gentry, and certainly not outside of Arcadia where they are strongest**, who can come even close to matching her one-to-one. Of course, the number of True Fae are...well, it's essentially infinite, so her deciding to One-Man-Punch her way through them would end hilariously badly. And if actually threatened and forced to actually give a shit...well.
** On earth they are powerful but Changelings have beaten them and even killed them. In the Hedge they are still more powerful. In Arcadia they are a nightmare, and best beaten by running, hiding, or using tricks.