I didn't even think about the elements placement on the periodic table, that's a really good point. Also, I'd rather not go with the traditional cliché, but it could come up from time to time. Maybe when they get in tight situations Chikara does something risky that saves them. While Umbra is utterly confused why he would opt to do such a thing, when she had seen several simple less risky options as possibilities. Eventually they could learn to work together and come to a better understanding, but until then Trixie and Eldur could act like peace keepers between the two.
I actually thought about having Umbra talk to the others about their pasts, and what exactly happened in the labs. As time goes on they could start gaining their own memories, and Umbra might just find some of her own that were suppressed.
Also, I've been planning on making another character, but yet again I haven't come up with any particularly good ideas. Updates on that later.