I haven’t fully fleshed this out quite yet, and the heart of the Black Swords is a well guarded secret that not even the Gods know of. The myth for now is that they were founded by mortal creatures, gaining a near-immortal curse to spread with a ritual and venom. How they got the curse is unknown, but they use it to only hunt the Yehkshir and remain invisible to the realms. Not even the Kuros know about the Black Swords nor have they seen them. Yehkshir are a more of a myth to the Kuros as well. Who started them is unknown, but the why is pretty clear; End the heart of the Kuros by killing the very things that garentee their return and dominance. They are not approved by the Gods, and gain their Curse in an unholy way.
Most are born into the Swords, as the curse isn’t hereditary and one must undergo a ritual to receive it. But of course, to gain new blood into their clan, every once in a while they stop to regain numbers and recruit new members. This period is often called Hearth, and can last for a hundred years or until it’s time for the Hunt again.
Any creature can become a Were, or a cursed were for the Swords. However becoming a Black Sword is a one way street, so recruiting isn’t the easiest, especially when they have to stay so secret. Once you’re a Sword, you can’t leave the clan. It forever binds those to hunt the Yehkshir.
Most of Niko’s group are wolves and wolf hybrids, given the original group were actual purebred Werewolves (the kind that cannot turn human, and who can infect others to become a weaker, untamed werewolf loyal to them). There’s different types of Were creatures, the Black Swords’s Weres are more of the curse kind, giving them a much bigger, resilient beastly form to fight with while having a smaller, easy to blend into society forms they usually stay in.
And for the last question, possibly! The Swords are typically anthro creatures, but it’s not strictly that, just any kind of creature from the Realms that happen to be recruited 😀 Though you wouldn’t be seeing any Kuros among them lmao, they don’t often hunt Kuros but they wouldn’t shy away from it especially now.
~Weird Hyenas