Board Thread:Speculation House/@comment-4830106-20131108040231/@comment-10390252-20140323164408

My headcanon at the moment is that Semblance is basically the ability to use the energy of their aura in a particular and extremely narrow outward manner. I suspect that it is decided mostly by personality and the person's essential nature. That's why all Semblances we've seen so far, to a greater or lesser extent, reflect the person's personality.

Once it is set in place, it cannot change, only be strengthened by practice and use.

Given the fact that Ruby has a strong Semblance at age 15, I arbritarily think it might appear fairly early in life. However, it remains weak without the focussed training that institutions like Signal provide.