The Pretons are animalistic, murderous, savages; at least as far as their neighbors are concerned.
Pretons are hunter-gatherers who live in caves, crude shelters, and natural formations. They seem to find man-made shelters worthy only of destruction; burning entire towns to the ground. They attack without reason or warning, demanding no ransom and taking no loot.
They practice no agriculture; hunting game and picking fruits and seeds and fungus. Stealing grains and pillaging and burning cultivated lands. They are known to be canabilistic and ritually sacrifce pretons and non-pretons to their dark gods.
They keep no animals. Not for food or companionship. Pretons kill and eat any domesticated animals they find, including dogs. They seem to take pleasure in hunting and killing domesticated animals, often leaving mutilated remains in easy to find places.
They do not forge metal. Pretons are a stone age culture. use wood clubs and spears, stone axes, slings and bows made of sinew. Preton raiders will use more modern weapons stolen on raids, but will not attempt to maintain or repair those weapons, using them until they become useless, then throwing them away.
They do not wear clothes, except as protection from the elements. Clothing is made of untanned animal hides. Thick enough hides are considered armor for game purposes, but these are only worn in winter, and never for the purpose of armor.
They are ignorant. Pretons are unable to read, and unwilling to learn. Their language is a crude and base version of that spoken by the Gaels. They paint cave walls and carve stone in shapes to convey scenes of nightmarish things they believe happened, or will happen.
Pretons love fire. They make fires for warmth, hardening their spears, and for burning down civilization.
Their territories are mostly in Wales, with isolated groups within several other nations. Any area with heavy forests is likely to have at least some pretons living within it.