From Ex illis wiki
The English Crown is the kingdom of England’s army, governed by Edward II while his father, Edward I, is ill. The young prince threw the court into a state of constant debauchery and gave control of the kingdom to his favourite, Piers Gaveston, whose only goal is to conquer Cornwall, which is now the property of Roger Mortimer. Gaveston actually left London with many royal troops, leaving the city to the hands of numerous enemies who only waited for yet another blunder from the prince to attack the royal capital’s fortifications. Thus, Thomas Plantagenet of Lancaster besieges the city north while Humphrey de Bohun of Hereford established west and William the Conqueror invaded the fields south of London.
It is in the middle of a city besieged from all sides that King Edward I comes out of his insanity. This miraculous recovery is a silver lining to a few lords who remained faithful to the English Crown. Londoners regain vigour in combat since they know now that the city is not alone anymore facing its opponents: the king stands by its side. The Ordo Magicum, an association of casters founded by Roger Bacon in 1301, comes to help the king, combining devastating magic power and bravery of the kingdom’s knights.
King Edward I gave himself the mission of rallying the rebel lords to the English Crown and to get rid once and for all of the Normans who have been occupying the south of the kingdom for several years now. But first of all, he must at all costs save the city of London from the disaster threatening it.
Cost to promote to Baron: +30%
House Plantagenet: French and English units cost 10% less to field, but Celtic units become special choices.
Ordo Magicum: Noble units and Heroes gain 20% in Magic power.