Board Thread:Speculation House/@comment-114.79.60.17-20160626164308/@comment-4010415-20170519013143

71.203.194.22 wrote: I think his semblance would be the ability to know exactly what someone's semblance is just by seeing it used once. With Pyrrha just by seeing it used he knew exactly what it was and how it could be used despite every semblance being unique and different. Of course it could be a semblance from a bloodline like Weiss hence how he knew, but if that was the case everyone would know Pyrrha's semblance by simply knowing her parents.

-Gypsybard But... Emerald told Cinder "you'd never know just by watching" because it took sparring Pyrrha for Mercury to figure it out. He figured it out because she used it to move his metal gun-boot. He could tell she didn't physically touch his boot, yet she was able to move it around at will. Therefore, logical conclusion is polarity. It doesn't take a "psychically know your Semblance" superpower for him to have figured it out.

Emerald: Her semblance is Polarity. But you'd never know just by watching.

Mercury: After she made contact with my boots, she was able to move them around however she wanted. But she only made slight adjustments.

Emerald: Just enough to make it look like she's untouchable. She doesn't broadcast her power, so it puts her opponent at a disadvantage.