The Welsh had a warrior society, and Wales was made up of small kingdoms constantly vying for power and influence over each other. Unlike 'Saxon/Norman' society, any royal child, illegitimate or otherwise, was eligible for the crown-making for many contenders for leadership and a fractious ruling elite well capable of murdering or mutilating their competition to get the power they wanted.
This retinue list allows you to make a 'pure' Welsh retinue or mixed retinue from the Early Medieval period to the High Medieval Period. The Welsh would ally with the Saxons or Vikings if it suited their purpose. After 1066 old enemies could be allies, disenfranchised Saxons would strike back at the Normans across the border with Wales.
This digital supplement contains 30 pages of rules for playing the Welsh in The Barons' War.
—description from the publisher