Make them "Light" dudes, or I guess in this case..."Darkness" dudes...They can shoot out beams of...er...darkness...that destroys all human forces in a region like the Light worked on inhuman forces, humans can't enter regions with a "Temple of Darkness" which would be in Zuma regions (Thereby preventing most interactions), and any human TLs in a region blasted by darkness would get an auto-critically wounded effect lasting...a long time. lololol
By the way: Totally serious here. The temples would be situated in three key regions, like Nightmarch, Dragon Song, and Ruins of Walfurgisnacht. This would probably be enough to reach all regions in the Zuma, thus frying any humans who are dumb enough to invade. As well, because the temples are immobile, that means the Zuma can't go out to fry people, and can only be strictly defensive. This would get rid of complaints about how they are out to conquer !@#$ because they seriously can't.
As well, this would make people who try to forge letters to instigate an attack fail, because the Zuma can't do anything about it anyway, and the guys who are the target certainly won't go into the Zuma lands, unless they really have a deathwish. And if they do, then it really is solely their fault and their stupidity.
Also I'm aware of generally how the Light works. Anaris can provide further insight, and yes, it requires a religion, elder priests, etc etc. Little modification here or there...It doesn't look like it'd be too big of a mod, since the "darkness" temples could even be reduced in its options (You can't sacrifice...wait, nevermind. Zuma...humans...sacrifice. Right, that can be kept in lol)
Unfortunately, this won't work either. It'll be perceived as unjustified for a small gain. I'm just trying to show that I'm not adamantly opposed to change. I also think about some improvements, but by now I've accepted that my ideas are generally crappy and won't be listened to.
Actually... this would be okay with me. Artemesia just had a not terrible idea expressed in largely reasonable terms. Woah.
Poll