Ancients
Characters that lived before the time of the clans.
Tribes are formed by a want or need to move to a new place. The intricacies of each Tribe is unique to that specific one, but typically are structured a lot like the clans with a leader, a leader-to-be, healer(s), Tribe members, to-bes, mothers, kits, and elders. When a cat wants to form a new Tribe, they gather a group of supporters and leave. They set up in a new location under a new name, and continue on as a new Tribe. On occasion multiple Tribes will settle next to each other, but for the most part each Tribe lives alone. They can split as many times as they want.
When a Tribe cat dies, they either go to the Tribe of Endless Hunting, the Tribe of Endless Shadows, or an in-between space called Limbo. Limbo is accessible to the clan cats, but is not used very often. When in Limbo, a cat must watch life play out without them, stuck on the ground until they come to terms with how they have led their lives, and how those still living have been affected because of it. Their actions while in Limbo tip the scales as to whether they go to the Tribe of Endless Hunting or the Tribe of Endless Shadows, though not all Tribe cats pass through Limbo first.
The last Tribe before the clans was the Tribe of the Setting Sun, founded by Lily of Deep Valley, hailing from the Tribe of Blizzarding Snow.