Soulbound Shifters

There's a nomadic barbarian tribe of shifters known as the Soulbound that roam the wilderness. At birth they are not tied to any one animal, but they still visibly embody animalistic traits: broad noses, subtle snouts, wideset eyes, sharp teeth, etc. Soulbound shifters are born with a greater soul than their body is meant to handle, so they have to find a compatible animal soul to share the burden.
When a young shifter reaches adulthood, they leave the tribe to go on a spirit quest to discover the beast that they connect with most. They must perform a bonding ritual in the light of the moon, and if completed successfully, their souls merge.
If a maturing shifter fails to bond with another soul before age 10, however, the curse will overwhelm the host and tear them apart from the inside out. Their mind is the first thing to deteriorate, then the body devolves, turning them into a raging monster. These unbound shifters are a plague to travelers and small villages, with a thirst for blood, not for gold. Adventurers are often hired to track down and kill these unbound shifters.
All shifters are cursed by the Moon, but they have their own methods of dealing with the affliction.

Culture

Culture and cultural heritage

Soulbound shifters are born with too great a soul for their body to contain, so before reaching maturity, they must bond an animal's soul to theirs to share the burden. Because of this, shifters are very in tune with nature and respectful of wildlife.

Shared customary codes and values

When shifters meet, it is customary for them to sniff behind the ear of the other person.

Art & Architecture

They are a nomadic people, so they don't usually have permanent structures. Generally tents made of animal hide, nice and portable.

Coming of Age Rites

Young Soulbound Shifters must go on a spirit quest to find an animal with a compatible soul that they can bond with, taking on its traits. If this is not done before their tenth year, they will begin to turn feral.

Funerary and Memorial customs

When an old Soulbound Shifter knows they are dying, they will go out into the forest and lay down to die, reabsorbed into the earth. If killed in battle or otherwise, their bodies are left in the wilderness to feed the wildlife and replenish the earth.

Common Taboos

When a shifter reaches maturity without bonding their soul with an animals, they go feral. Although, there are some shifters who ride the line between feral and soulbound by bonding with small creatures, spread out over time. These tiny souls of mice and rabbits feed the beastial soul inside, but are not enough to truly satiate its hunger. This practice is looked down upon by most Soulbound shifters.

Ideals

Beauty Ideals

Elegant, strong, and prominent horns, antlers, teeth and claws. Interesting coloration and patterns in fur.

Relationship Ideals

When Soulbound Shifters do mate, they mate for life. It is not uncommon for them to live totally solitary lives, which is why their population is remains rather small.