The look of pure happiness that Isa had was enough to tell Maria and Clark that this was the correct choice. On top of that, it was clear that she had been secretly looking for another beast. She had the ability to allow her beasts that had elemental natures to fuse with her body. Due to that, Isa had the ability to become stronger physically in ways that other tamers would be unable to do.
"I thought that I would need to find an earth sprite or something else. But this is great. I bet I can even help it learn the crystal armor skill!" This was not what Calrk had thought of.
"I think I have heard of that but I didn't think of it. How would that work? Would it still fuse with you?" Since Clark was not adept in the ability that Isa's family had, he had to ask. His system could do nothing to explain this to him either.