I just tested them in RMXP so I can report accurately on what I find wrong with these character sheets.
Lets start with the first one, the dark knight on foot. You are correct that he animates fine, but my complaints for this one are about the looks. On the front view, his hands and some other parts of his armor are redish for no reason. On the side views this also happens, though only in part of the hand/arm. For the back view, the cape isn't aligned right. Its too far to the left and looks rather akward.
Next, the mounted dark knight; again the red armor problem appears... I don't know what program you used or how you attached the cape but I imagine it is related to the process you used. The lighting of the helmet shifts akwardly in the front view, but otherwise, compaired to the other views, animates relativly well. For the side views... When he is going left the way he leans forward and moves around while he rides doesn't really look right. And this time the helment distorts strangely, getting smaller and larger. In the right view he looks a little more natural aside from the way he moves his legs. It makes it look like he is trying to walk while riding the horse. The helmet distortion shows up in this animation as well. The back view is argueably the worst. It at least stands out the most. The cape is still unaligned, which isn't surprising as I imagine you just used your on foot sprite. He jerks around back and forth while you move, and it looks just terrible.
And lastly, the catgirl sprite. For starters, the hair coloring is just ugly. You should try to add more contrast, and perhaps pick a diluted yellow that looks more natural. When transitioning from side to front or back, it hardly seems like you are looking at the same character due inconsistancy with the things on her head (Ears I guess). The animation is weird from all sides except her right. She seems to wobble back and forth a tiny bit from the front and from the back, and again her head seems to shift a bit, probably because how you created them. The head should be consistant between frames, or else it comes out akward. When she is walking left there is a little twitch in her step, though after the front and back animations you hardly notice it.
Please don't take this as a personal attack, I just don't think anyone wants to use buggy sprites. I am not saying my sprites are perfect. In fact, they are far from it. I noticed a few things I plan on going back and fixing after I posted them. I just thought that I should point out the errors in your sprites, many of which you probably noticed yourself, so that you may go back and fix them, or take them into account and make better sprites in the future.
The battlers on the other hand, I think are pretty cool, though battlers are certainly not my area of expertise.
(And sorry to correct you, but that isn't really an alteration of the main sprite (Arshes), however this is not the topic to discuss that in.)
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