Two bits. First, the topic du jour, Keelyn.
...Think of the things those demons must have done to her to slowly condition her. Like that imp in her 'pedia entry who manipulates her into summoning him herself...
I've mentioned this before, but I've always seen Keelyn as the brains of the operations. She's the daughter of a powerful telepath, and while she isn't formally trained, she's proven a powerful sorceress. She probably influences her demonic henchmen as much as, if not more than, they influence her. I love the image of the fierce servants of Hell being unwittingly transformed into the playthings of a girl who doesn't fully grasp her own power.
So the Mimic unit. Are we to assume they have this ability because being trained to fight in the arena, Balseraph swordsmen grow to be able to adapt to whatever their opponant throw at them? Or is it simply because the carnies are that good at copying the movement and manerisms of others, like a great actor?
I see it the carny way. They see their opponents fighting better than they do and, mostly for their own amusement, copy that new "trick" exactly. But they remember what they've learned as well and use it on their other enemies. Although perhaps, since we're talking about the Balseraphs, a weak form of mind reading is involved as well; they might literally steal the skill from their foes' minds.
I can see the Mimics being a slightly irritating foe either way.
Imagine you're a Bannor soldier, and you suddenly see a perfectly ordered legion. Except their colors are bright and flamboyant, and the soldiers are grinning like it's some sort of hilarious joke... then you see one raise the Balseraph banner in parody of the ceremonies used to raise the Bannor one. Your own legion attacks, expecting them to break ranks like the clowns they are... but they just smile even more and prepare, in Bannor fashion, to meet the charge. And suddenly, you're the ones breaking ranks, panicking at the thought of facing an enemy so perfectly trained in Bannor tactics. And the Balseraphs prove better Bannor then the Bannor themselves by, in perfectly regimented fashion, splitting off to encircle and annihilate you, not giving up the mimicry for even the briefest second.
I think I might have written a rough draft of the Mimic Pedia entry... unless the team has plans already.
I also see them holding the parody of whatever they've faced in every moment, even when nobody is watching. Mimics impersonating the Doviello would be just as fierce and wild as them, swinging the bodies of their fallen foes with ruthless brutality in battle and feasting as the Doviello do after the battle. Of course, everything would be a parody. If a Bannor ceremony required the lighting of a flame, the Balseraph version would do so with a fart. The Balseraph version of a Doviello feast would take almost as much influence from a hedonistic masquerade as it did a pagan feast; its centerpiece wouldn't be a roasted boar, but some stitched-together amalgamation of pig, cow, dog, and human parts. Ones who learned their tricks from Elohim monks would make ridiculous pilgrimages to various brothels as a real monk might to holy temples and give ridiculous but worthless trinkets to the poor of the Balseraph people where a real monk would give money.