Blood Eagle quickrun(20ish hours playtime)

[NachtRitter]

I got screwed out of the achievement due to saving, sleeping and loading the next day. Probably should've read the patch notes instead of assuming that they had fixed it. However, my experience shows how quickly it can be done. Here's how I conquered brittania by 930AD.

Start as Ivar the Boneless

Immediately call your dynasty members to war on the Sons of Lothbrok Invasions

Train 4 regiments of bowmen men at arms, level them up to rank 2(you can do this with 3 of them, leaving the 4th at rank 1 for now)

Combine your armies, take chivalry focus on martial, lead the armies yourself and focus on east anglia(this is because halfdan's armies in northumbria will be hostile to you and you can lose a huge chunk of your strength if you aren't paying close attention) DO NOT RAISE YOUR MEN AT ARMS YET

Immediately upon maxing out your men at arms pause the game, raise them, and get ready to go into serious negative prestige. Pause and declare war on EVERYONE EXCEPT MEATH in ireland with conquer county focus - ireland has no duchies aside from meath, and only meath is allied to alba, so you won't be suffering much.

Set to speed 1 or 2 for this part so you dont have to pause and unpause constantly. Good now call your dynasty members and allies to every single war you just declared. You should now be at around -1500 prestige.

ALWAYS EXECUTE your prisoners during the conquest of ireland, you need maximum dread and minimum marriage prospects left to force your new subjects to accept matrilineal marriages. by 890 you're King of Ireland, however your prestige is terrible. If your wives aren't pregnant, kick them to the curb and marry young fertile things, as soon as they are pregnant do it again. You need a lot of kids for this. You're going to marry them off to every surviving noble in your realm, and spread the titles you gain over the next half century among as many Ivarings as possible, so that there isn't a single possible ruler who isn't house Ivaring in the succession.

Switch to authority focus now that you're a king, someone else can lead the armies - usually a good way to get rid of straggling o'neill's after you take meath. Spend a ton of time converting culture to norse all over ireland(becaue your heir will most likely be diplo or steward and suddenly the peasants are going to be very unhappy with a foreign ruler), I moved my capital to Waterford, started there. Don't worry about religion until the next player heir, who you're going to want to convert to Insular Christianity - letting you keep 3 secondary wives instead of concubines is a big deal for the blood eagle achievement, because you have to keep an Ivaring as your player heir at all times. Whenever possible use scandinavian inheritance succession law and boost tribal authority. You wont be declaring wars for a while, but you can still get some rpestige back by joining in wars your brothers call on you for. After your heir converts to insular they wont call on you much, if they do you can decline.

Keep up a steady stream of county and duchy conquests picking away at everything but staying away from major opponents. In between wars keep a constant stream of raids going, keep a couple of big armies for raiding so that you can crush their armies and keep them weak for the next war. I let Alfred and Halfdan wear each other down in constant back and forth wars while I slowly subsumed Mercia, Northumbria and Wales. DO NOT FORM NEW KINGDOMS until you have the requisite 73 counties to form Empire of Brittania or the partition laws will break up your empire. Until you make them into kingdoms you'll just have more duchies under the Kingdom of Ireland.I waited until the last for Alba and simply invaded and subjugated their King, executing all my prisoners as I went then formed Brittania.

I kept control over Duchy of Leinster(since I set my capital in Waterford, which had a higher fort rating than elsewhere in Ireland and the two counties within it as well as kingdom of ireland, these passed to my player heir with everything else floating around between Ivarings.

Your life will be much easier if you convert faith to insular and culture to norse everywhere in your empire as you go.

[MrT]

I got it by 909 starting with Ivar (I also had a good run with other brothers pre-patch but achievement did not fire).
I conquered Scotland and a few duchies in England, then the majority of Ireland, remaining a pure viking (i.e. not converting yet).
Then the Pope calls a crusade against England (happened in my 2 runs), which I use to convert to Catholicism and join the crusade (which will do the mopping for you). Even if you don't get land after the crusade, you can easily kill the new crusader king and get his land.

That was my favorite achievement btw.

[NachtRitter]

I tried the alba run first, but it's risky, if ivar gets killed you're stuck with elective monarchy and the achievement spirals out of control. Haven't seen the pope call crusade yet, although I did have jihad declared. On a side note, after getting screwed out of the achievement I loaded the game on a whim and grabbed another achievement by quick converting to Adamitism(Christianity) and it's like the game got slapped in the face and said 'oh yeah, here's your new clothes Mr Emperor, and a Blood Eagle too' - which is how I got Blood Eagle and The Emperor's New Clothes in one run :P

[MrT]

A naked Ivar performing the Blood Eagle on his ennemy ... what a sight

[Mikebrowski]

So my ivar died right before I mange to get the empire and still didn't get the achivement are you meant to do this with IVAR? and or the danish/swedish king?

[MrT]

Nope it works with the heir (you only have to start as one of the available 4 characters). For me It was the first heir that got me the achievement. However I have no clue how the heir was selected ... It changed every few months (probably due to Alba kingdom)

[Mikebrowski]

If the save is old though, it wount work right? I am trying to find the patch that states this... I sadly didnt get the achivement and just manged to conqure the entire british island... dammit

[NachtRitter]

Has to be a descendant of ragnar afaik, started as Ivar myself, his grandson Ivar completed the conquest as an Adamite Christian, then I threw all the lower tier realms on elective succession for S&G. I'll probably pick it up later and try to crusade for the holy lands :p Right after I do Rurik, APC and Mother of Us All.

[Mikebrowski]

My save was from before any of the 1.1 it was one of the early versions what version changed this? Does someone know its not the recent https://forum.paradoxplaza.com/forum/threads/ck3-dev-diary-42-1-1-patch-notes.1428193/

Which one is it?

[NachtRitter]

Shrug, I did it just recently on the latest version(1.3.1) since I've been busy with HOI4 and Stellaris and just haven't got around to playing much before this last week :p

[MrT]

@NotMeHow
Yes if your save is old and your Ruler is no longer the initial character then it won't work. Happened to me with my first run. You need to restart the whole run ...

[Zornvel]

You can also play the long and super safe game chose Ironside, create Sweden, then Scandinavia and then conquer whatever you want, it's pretty hard to get in any danger if you follow this way. But of course it's the longer way.