An American CKII player who was introduced by a friend.
Clan Mac Gabráin (Dál Riata)
From a two-county petty kingdom in 769 ruled by King Áed III arose the great Kingdom of Éire. Defeating an early attempt at conquest by Urguist the Usurper of Pictland, Dál Riata rapidly expanded into de jure Ireland, and waged holy wars to seize Iceland and liberate the Orkneys from the Norse, even driving into the heart of Pictland itself to seize the capital at Circinn. Finally in 848 AD, under Eochaid V, known far and wide as Eochaid the Wise for his careful stewardship, the northern half of Ireland united under the green. In keeping with his moniker, Eochaid proved a shrewd, practical ruler, vassalizing Irish chiefs with the force of his personality when possible, and the might of armies and strong ties with House Iceling in Mercia when not. Éire stands now as one kingdom, controlling half of Scotland, all of Ireland and Iceland, the Welsh Duchy of Deheubarth, and even a foothold on the Continent with the northwest half of Brittany.
Since its founding, the Germanic heathens have twice attempted to regain their foothold in Scotland, with successive Danish kings invading Pictland. In both invasions, while lesser British kings united to hold the Vikings at bay, the seafarers of Éire set aside their longstanding enmity with the Pictish kings of Clan Circinn and took the offensive, landing armies deep in the heart of enemy territory, capturing capitals and taking many prisoners, crushing disorganized enemy warriors with their unstoppable gall oglaigh knights.
And Mac Gabráin has a lot of wacky fun with Jews:
So, middle of the 780s, I'm off pillaging Galloway or some such nowhere place, and my steward calls to report an accident on a construction site in Innse Gall, my capital. I swear up a storm in Gaelic and keep raiding. A few days later, though, my spymaster Gedalyah Ben Ari calls me into a meeting, says he knows who sabotaged the training grounds (?). It was the local bishop, Ainmere, and I assume in retaliation for me firing him from court chaplain in favor of somebody smarter. Ironic, isn't it?
So I order Bishop Ainmere arrested, but the sheriff botches it and he escapes and starts a rebellion. I'm in no mood to deal with him, and fortunately I don't have to: at the ripe old age of 70, Áed III has spent fifteen years being a dirty old man. He has seven legitimate children, one legitimized bastard, and one regular bastard, and they're married into royal houses all over Britain and France. I also have two tributary rulers. So I call up my neighbor Owain of Strathclyde and gesture angrily at Bishop Ainmere, and Owain runs right over to Innse Gall with 400 troops and drags Ainmere out of his hidey-hole.
Gave serious thought to beheading him, but then I decided to be merciful, for a given value of "merciful", and instead forced him to ransom himself to the tune of 26 gold.
So a few years later Áed has kicked off and Eochaid IV has taken power. I learn through my spymaster that my cousin Caustantin, whom Áed made Chief of Ulaidh after the conquest, is trying to have Bishop Ainmere killed. Hey! No skin off my nose! And I've already got a successor in mind: the spymaster who put me onto Ainmere in the first place. That's right! Gedalyah Ben Ari... a converted Jew!
Creating a Jewish-ruled duchy out of the Isle of Man
...through a grant of conquered lands in gratitude to Chancellor Rava of Ouallam, an Ashkenazi Jew who turned up in my court one morning. While not exactly useful in the long run it had some strange effects on the landscape of Britain, with Duke Rava II of Galloway ultimately killing a mutually hostile king of Pictland before succumbing to a holy war by Lothian and fleeing to Austisland... which at the time was ruled by a Catholic Ashkenazi lord also put in place by me.