So, because it's one of the areas I've so far played the least in (really), I decided to try my hands at a Byzantine Empire game. Started in the CM start as the count of Arborea, Italian Catholic Euphemio Oristani. I managed to take over the other province of Sardinia, Cagliari, within the first 10-20 years, but after that found myself stuck there as count under random viceroy duke lieges, always of house Isauros. I was employing a strategy where I was running Seniority, educating everyone with intrigue and always alternating between seducer and stabber characters. Spam marriages with one guy, then clear out the higher claimants with the next. Easier than switching focus because I tend to forget about that. Because of my low rank and dynastic prestige, I didn't get a great deal of
good marriages - once I was close to beoming king of Serbia, but then Serbia got annexed.
At what I think was my sixth(?) character, the duchy title finally ended up in the emperor's hands for longer than 2 milliseconds, and I clicked this button I had honestly never clicked before: demand duchy from liege. This shifted me into Gavelkind and shortly after, a childless daughter in her late 40s inherited. Homosexual dad in his 70s had managed to have another baby daughter from his new wife though and failing that, I would have inherited the barony of Tusculum, so it wasn't all bad. My stab-seduce scheme broke at this point though, can't make a lot of bastards of my dynasty with an old woman. Change of plan was needed.
I had lost my home province to the Lombards some decades ago, but upgraded the Castle in Cagliari piled up lots of money throughout the years. There was medium CA, but the emperor had just lost an invasion of Armenia to the caliph (by the way, the Abassids lost that to a bastard dynasty of theirs not very long into the game, this Hasan dynasty fell apart through a decadence revolt... still larger than in normal start dates (honestly, 769 has to be my least favourite start there is,damn blobs... though this game turned out very 867-esque), but they lost Egypt, a lot of Persia and some parts here and there.
Anyway, the emperor had lost this war and, dumb as he was (really, he was slow), had a -180 or so penalty from held duchies. I have no idea why he was holding these duchies, but there was a 700% LCA faction, and I joined. It took seemingly forever to fire, but victory was almost certain with 28000 against 8... except that apparently our leader got captured in the first actual battle (I have no idea why else it would have happened that way), lost the war, I got my only county revoked. And it was granted to an Isauros.
That was the year 888. So, how successful had my family spreading been so far? A couple barons. Counts of Friesland and Naxos, Strategos of Split (now I think just count again), count of Catanzaro under the lombards. And, since 878, the duke of Poitou, Bounconte. I became this duke, who currently was in rebellion, to depose the last independant Karling with some guy from house Louping. WF had some severe viking problems so I actually came close to winning, but when Venice intervened, the war was over. Didn't have my title revoked though. I spent the next years plotting internally, removing my vassals' domestic alliances and taking their counties. Meanwhile, the last two Karling rulers were squabbling for the throne of WF - there was the rightful Godefroy branch, Godefroy I was king when I became duke, his descendants had the same name. And there was that guy's great-uncle Charles II, genius count of Vermandois with 31 Intrigue and a lot of bastards.
After I had taken control of Poitou, I decided to install this AI favourited Louping claimants' Carles son Gaston, because he would have no meaningful allies. So I fought him into power, converted from Italian to Occitan, betrothed his daughter to my nephew (meanwhile, I also had betrothed my son to the 2-year-old duchess of Normandy... and he died. So I broke my other sons' betrothal... and the duchess died under suspicious circumstances at age 15.)
Then he had a son and I realized I couldn't expand because of Crown Authority, so I declared war on him to take the county in question (actually was part of my duchy, but directly under the king) and reduce CA in one swoop. Before the war was over, he surrendered to another faction and Godefroy was back in power (which reset my battle war score

)... but then he died and his 15-year old black son (Participazio doge of Venice, see aforementioned alliance, had a Mandé wife once, no idea how but the genetics lasted a few generations) Godefroy II was the one to surrender to me. Just to have a faction pop up to get some other Karling into power by the duke of Orleans, a son of Charles II. Because he had a lot of siblings, I didn't want that, invited him to my court, made him a monk and tried to kill him... only later I noticed he was a bastard. Oops.
So Crown Authority was raised again because my CB didn't block that apparantly, and I was still having a truce... so I killed the king, and fought one-year-old turkish-looking Godefroy III to get another one of Charles III bastards into power, who later became Charibert I de Dreaux. Only later, CA had been raised again so I was looking for what factions to start, I noticed that my Pictish wife Elaine Uib also had a claim on France, maybe she didn't have it while her father was alive. So I started another war to get her into power. Of course she gave it up within a year to another guy from Charles II line, a non-bastard called Loup. And then I got maimed from an event, died and this is where I am at the start of my third character's reign since the exile from Sardinia:
My border is the Maine-Tours-Bourges line. I can control and depose the French king almost effortlessly at this point (earlier I was needing mercs and still had some close battles) as despite lots of siblings, he has no good allies, only the duke of Normandy trying to beat up Vikings is dangerous to my forces... but if he surrenders to the eastern dukes, I can do whatever I want and still have my plans foiled. Valois is currently independant under Godefroy III who completely hated my father duke Pagano's guts for killing his father and taking away his crown but apparently is okay with Amaneus. Mother is 59. All I have to do is depose Loup for her again, and inherit. Maybe I'll faction for Primo first, so I won't have to go to high CA to get that. Elective is too risky as I'm Occitain and the other dukes are all French...
But from my original goal, I'm farther than ever. The Alachaisling (Lombardy, Saxony, Burgundy) and Hetanid (Aq, Germany) kingdoms are very reminiscent of the 867 Karling fractured mess... and both are stronger than France and in the way. I want to take revenge and destroy the Isauros to the last man, but their numbers and dynastic prestige are through the roof, I won't be able to take them on for a long time... Also, this has Sunset Invasion on, so that may become a problem as well.
I will also try to remove my other landed kin, as most of them serve the enemy... Poitou is the new home. Also, recently I had a game where I accidentally got my dynasty onto the Byz throne, and they changed my colour on the dynastic mapmode and kept calling me into pointless wars, that was annoying. And I don't want my dynasty screen to lag from 5000 members.
World:
Interestingly, both Sardinian counties are currently independent. Didn't know that. Still controlled by houses Alachaisling and Isauros though. Bulgaria got a liberation revolt (will probably only last a couple decades), slavic Croatia made a resurgence and I think Crimea also was under the blob before. Nice. Valencia is Norse.
Still, besides the dynasty names and cultures, this isn't terribly far off from the way the 867 start would turn out, unlike most 769 games where the world is split in 5 empires by Karlings, Sviþjod, Umayyads, Abassids, Byzantines with just some little pagans, Indians and Brits independent at the very far edges of the map.