This mod deals with feudalism adding an interresting new mechanic based on legitimacy.
I recomend you start eighter with francia when it is huge and then use the cheat code to lower legitimacy to 50 so the event for its partition fires, any date after is cool to.
Be prepared to deal with jealous brothers and crazy sucession wars , also be wary of ambitious vassals.

Link: https://www.dropbox.com/s/okwt6qxgl4dnaed/Dank%20Dark%20Ages%20ET.zip?dl=0
You know the drill just extract that into the mod folder in Documents\Paradox Interactive\Europa Universalis IV\mod

Scren Shots from a game started on the 350 bookmark, the hre formed to(Old version).
http://postimg.org/image/65pqtd0c5/

http://postimg.org/image/pouc2pz3p/

http://postimg.org/image/swytfrldh/

Features:
-Redone some country forming decisions so france and andalucia don't show up to early
-Some country exclusive events particulary for the carolingians and the spanish
-Mediaval cultures now appear over their roman conterparts.
Ex. Gallian--->French,Burgundian,Occitan, et cetera
-Ability to adopt this cultures as a barbarian that whants to claim that dope roman glory
-West slavic cultures are created if any slavic culture group per say invades germany the wends,among others, whould spawn.(The Germans must fear the Slavs)
-Crude Blow up mechanics for the muslims of Spain
-Better than CK2 Gavelkind :D
-Vile Vassals that will demand autonomy if your legitimacy goes to low
-Redistributed some unit models for flavour
-Hability to claim old roman provinces for barbarian tribes to help making reasonable borders.
-Now the Auto anex feature is available to all hordes wich get a 6 military leader, while he is alive that is.(Every one shall fear the horde)
-After the barbarian invasions start the german cultures will change, also prussians and pommeranians will spawn in their respective places.
-Ability to settle down for hordes, anatolia, carpathia, bulgaria are the potencial targets for this, their governament, unit type, techgroup will change and they will change the culture of all provinces within the land they are settling.

Know issues:
Some countries will spawn catholic/protestant before the schism, some will spawn chalcedonist after.

To be done:
-Expand the number of potencial vassals and kingdoms for gavelkind(Currently covers from portugal to russia but i plan to include minor asia , caucassus , north africa and india/indochina )
-Redo the code so it does not grant cores to land you don't own to countries that split from you , i am just lazy to it.
-More unique events for countries
-Something like the mongols for the Almoravids and the Almoads
-Crusades maybe?
-Balance

On a final note i ask of you ideas for unique events