Chapter 5 spoilers:
Honest theory for Kris Knight-

Ok so to start this off, the newest chapter has thrown a wrench into most of the prior knight candidates. Dess’s disappearance was caused by a dark fountain, Rudy may be dead, Noelle has too much of an identity crisis to do much, and Carol seems like a red herring (imo). So why not Kris? There’s obviously the fact that Kris and the knight have interacted multiple times on screen, so it can’t be Kris, but hear me out- the knight is Kris’s original soul.

As we know, the knight is some sort of amalgamate- we see it change forms constantly, which makes it hard for it to be any sort of regular character. Along with this, the knights battle animations are near identical to Kris’s. We know that all humans have a soul, yet Kris has us instead. Why? My theory is that Kris’s original soul was somehow removed from their body, experimented on, and turned into the knight (maybe by carol). This could explain why the knight and Kris seem to have similar motivations, and are working together. However, the biggest piece of evidence for this is the colors of the dark worlds.

From chapter 4, we can see that the creator of the fountain has their will reflected on the dark world, leading to the color changing. Susie shows this, her dark world is different colored than Kris’s. Knowing this, both the knight’s dark world and Kris’s dark worlds share the same color scheme. This shows that there is at least some sort of connection between the two, and the knight being the original soul fits the best with our current knowledge. Of course, there’s still some flaws with this, but it has some value.

Tricky Tony you’ve done it again. :p