Kingdom of Dyflin is an expansion to The Great Heathen Army. That game was a collection of Viking land battles set in what would become England. This scenario book expansion provides four new battles set during the same period in Ireland, utilizing the maps and counters from Great Heathen Army.
Cenn Fuait (917) finds the Irish on the offensive until the sudden arrival of enemy reinforcements turns it into a desperate rearguard action. Ath Cliath (919) sees six Irish Kings band together in a disastrous attempt to break Viking power. At Glen Mama (999), rivals Brian Boru and Mael Sechnaill join forces against the rebellious Mael Morda and Sigtrygg Silkbeard, with Dublin as the prize.
And finally, there's Clontarf (1014) - one of the most famous battles in Irish history. This is the big one, folks - the biggest and longest battle in the entirety of the Shields & Swords II series, sprawling across two maps, with over fifty units on a side.
—description from the publisher