The Ikko Ikki are religiously inspired rebels.
Ikko Ikki may emerge at random at a district where a riot has occured. The odds of emergence of Ikko Ikki tend to be higher in districts with a famous temple.
Once Ikko Ikki are established in a district they will wield armies, to defend their towns, these armies are not used in offensive campaigns. These armies tend to be rather weak and small, but their towns are often heavily fortified. The Ikko Ikki tend to build high level castles and temples in districts where they have been established for some time.
Their temples and castles are unlike those of other clans, and only occupy one district. They do not hold the surrounding land.
Ikko Ikki who are left unscathed by war, may spread to neighbouring districts. This spread is done unopposed. They tend to spread like an oil stain. If the Ikko Ikki are left untouched, their territory will eventually get larger and larger. As their realm increases in size, their spread will be more rapid. So it is best to take them out early, if they are near you, or else they can become a real nuisance, as they will begin to take more and more of your land until eventually there may be nothing left.