Adventurers. They are everywhere with thier 7k armies. Especially with the 2 first bookmarks, where there aren't many big realms and/or are being split very quickly (Karlings and Abbasids). Most of the realms don't have big armies and all adventurers are guaranteed to win. They conquer all their neighbors with their event spawned army, then get conquered by other adventurers as soon as their heir inherits and loses event army.
It's rather unfun to see potential growing regional powers crushed by random adventurer that never had any land and conjures 7k troops out of nowhere. Only realms that can fight them are growing (AKA Byzantines, but I'm also seeing Constantinople taken by random khitan guy) and the rest is just colorful mess that never unites, because it doesn't have enough time to grow enough before being struck with another adventurer.
It's rather unfun to see potential growing regional powers crushed by random adventurer that never had any land and conjures 7k troops out of nowhere. Only realms that can fight them are growing (AKA Byzantines, but I'm also seeing Constantinople taken by random khitan guy) and the rest is just colorful mess that never unites, because it doesn't have enough time to grow enough before being struck with another adventurer.