I created a second knight. I intend to keep this one in the Rescue Camp to greet friends, so it's not THAT big a deal gameplay-wise, but... how the heck is mist energy shared between knights? It's collected and stored by your armor... so all the knights on my account share armor? But it looks different and doesn't share stats...
Crystal energy being shared is somewhat odd, but it's a thing. Things can be passed around, or stored in a locked container with multiple keys, or whatever. Plus, it's based on real money, and that gives it some slight 'reality warping' abilities without totally shattering suspension of disbelief. But the shared mist energy pool just doesn't make sense!
I don't think you should try and make logical sense of it within the context of the game's story. The game is designed in such a way that you don't NEED multiple knights; if they didn't share mist energy, you would have a disadvantage by only using one knight because you could be using the mist energy of the other two knights to triple your output. Do you really want that?