This is what I have for the Fir'Selyth. Let know if I contradict myself or make a glaring mistake.
The Birth of the Fir’Selyth Clan
Legends have it that the clan began when the first of the Fir’Selyth found the Patient One asleep in the deepest recesses of one of their forests. Upon seeing the deity their bodies began to bend and corrupt in alien ways. At first they were horrified, but within a fit of madness they accepted their new forms as their own. They captured other elves from the neighboring forests and dragged them screaming to the Patient One. They too became a thrall to the monster.
After being converted to the beast’s way of thinking they began to build a tower to house the Patient One to let the deity sleep until it awakens to destroy the world. After generations and generations the Patient Ones influence waned and only the mutations stayed with them. Their minds were their own, but they were still taught how the god had gifted them their bodies, and of how they are stronger because of them. Anyone born without a mutation was carried to the tower and sacrificed on the stone slab, where the blood would seep down to the deity below.
As the tribe branched further and further out they found that it was impractical to drag their ungifted to the tower, so they burned a sacrificial circle into the ground where the blood would spill. As food grew scarce they found themselves eating the ungifted after bleeding them on their killing grounds. They reveled in the eating of their sacrifices, and soon it became common practice to eat their dead, just as others would eat animals.
Some Fir’Selyth Clan Beliefs
If someone is born without mutations they are given time to show their gift unlike in the past. Everyone from the age of ten is trained to fight, and they will often have duels with each other to sharpen their skills. If by the fifty they fail to show their mutations they are exiled out of the village and are thrown into the wilderness. If they don’t leave the forest within the first day they are hunted down to be eaten as if they were an outsider entering their territory. They don’t kill them however, they capture them then they hang them until they die in the center of the village, roast them and eat them, and only sometimes in that order. After all of the ungifted are either killed or long gone the taught the art of tracking prey, specifically other humanoids.
Their mutations are highly respected within the tribe, and are what makes each one of them unique. At the age of 80 there is a ritual where they take a needle and carefully bleed the skin around their mutations in intricate patterns. Their aberration blood is different from elf to elf, but it is often tinted at least the slightest shade of violet if not darker. The more tattoos they have the more respect they have within the community. On the other hand any traitors that are found have their mutations cut out by force before throwing them out into the woods, still conscious or not. Very few traitors live through this process, but it has happened before.
Unlike other tribes they don’t hunt for meat, and unless they happen to kill someone they don’t eat meat at all. All members of the Fir’Selyth are taught to forage for plants to feed themselves and those that they care for. If they are willing to forage for plants on someone else’s behalf it means that they have respect for the individual. Animals don’t often endanger the lives of the tribe, so it has become taboo to hunt them for their meat. Humanoids however are considered free game if they are either in their territory, or threatening the lives of someone else. Other elven tribes, such as the Tyrmitore are considered rivals, and the Fir’Selyth will occasionally encroach on their woods for plants if food gets scarce. Challengers are met with blades, and they often became become food for the Fir’Selyth if they weren’t prepared to fight them.
The Fir’Selyth are known for their strength and speed, as well as their relentless attacks. When faced with opponents the Fir’Selyth don’t back down. If an enemy escapes them it is their duty to track them down, stalk them, and call out to them with their inhuman hunting calls. It’s unacceptable to leave the hunt without being sure that you can’t catch up to your prey.
Jobs within the community are scarce, and they are largely independent simply because they keep their lives simple by living an almost feral life. Traditionally all of the elves are trained to be trackers, but within the last 400 years weavers and blacksmiths are being accepted into their communities, supported only by the plants gathered by others in return for their goods. The decision to craft is a hard one, because if they are bad at their trade they simply don’t eat since no one wants their goods and they aren’t knowledgeable about the plants as the trackers.