Affinity Purists
This mod adds 6 new (free) Society Traits which grant major bonuses to your civilization while you are playing single-affinity games. Tomes other than the purist trait you have picked have an 80% research penalty.
Known issues: playing Barbarian Chaos Purists allows the player to select bloodlust twice (they do not stack, so do not pick that trait unless you want to waste a level-up)
While each affinity purist trait has several minor advantages, each has at least 1 change that more dramatically alters the way your units work.
Shadow: Your units gain a range 2 minor phase ability (for backstabbing and positioning)
Materium: Your melee units gain a 1-use only javelin that places them in defense mode. Your ranged units gain a dagger sidearm
Order: All your units can pray once per battle for a 10hp heal, cleanse, and intimidates nearby enemies.
Nature: Your magic units can summon a vine once per battle.
Chaos: Your units gain Bloodlust and Vicious Killer
Astral: All spells cost 20% less mana and casting points. Your ruler can summon an amplification pylon.
This mod will be tweaked and balanced over time. Ideally, each affinity will accumulate at least one more tome at each level in the future which will help you not "stall out" once you complete your research tree. Once this happens, I may make a more toned-down version of this mod since players will not be so penalized for forcing themselves into only 1 affinity’s tomes at that point.
update 1: changed chaos bonus from killing momentum to bloodlust.