Not so much villainous as brilliant realpolitik in action, out-gambitting one of my dukes to remove a persistent thorn in my side. In order to deal with a bloated Duchy of Dál Riata left over from my wars to create Ireland and weaken Pictland (by now held as a secondary title of the Ard Rí na hÉireann [High King of Ireland]), I used the duke's plot to kill some random nobody in one of his earls' courts as cause for imprisonment. I was at about 40% success percentage, and failed, causing the factionalist moron enthroned in Goblaraidh to go into open revolt... exactly what I wanted.
Irish and Wessexian troops swept into an oversize duchy combining Breifne, Airer Godel, Dail Cluiadh, Athfhotla, and Goblaraidh, and trounced the rebels in two decisive battles before capturing the rebel capital, emptied of its levies due to the war, and the duke was forced to surrender despite a belated request for white peace. In short order the former duke was reduced to a mere earl of two widely separated counties and dropped down an oubliette (he died there less than a year later and his prepubescent heir became a ward of the king), and Airer Godel and Dail Cluaidh, held by a single earl, became direct vassals of the Ard Rí na hÉireann. The only thing left is to find some specious excuse to revoke one of his heir's counties.
Oh, and remember that Earl of Cataibh I life-ruined earlier for trying to cuckold me? I checked the oubliette and he was somehow still alive, albeit having been reduced to a gibbering lunatic. Satisfied that he was too loopy to be a threat anymore, I released him and he ended up reduced to being the Steward of County Laigin, a subset of the Prince-Archbishopric of Laigin.
There's only one rule in Ireland: Don't fuck with King Rian.
