The story:
As your king marches across the Arabian desert, he decides to leave you, his most trusted captain, behind at the Oasis of Caleron with a small detachment of troops. Your mission is simple, but not easy: Deny the use of the Oasis and the river that feeds it to all the King's enemies, and build up a secure base that will eventually become the capital of a small kingdom your master will bequeath to his oldest son, who has joined him on this holy crusade.
I tried out this skirmish with the Wolf, Saladin, and King Richard. Saladin and the Wolf built huge castles. If you like it 'big', then this skirmish is for you. I think a 2 on 2, with the lords above the oasis vs below the oasis should prove interesting. I allied with Richard below the oasis, and it was bloody good fun!