Board Thread:Speculation House/@comment-27883360-20160305074527/@comment-28046957-20170125231011

I think his semblance is more of him being able to turn off his negative emotions? Because it's canon that Grimm are attracted to negative emotions. Ren was panicking before activating his semblance, but then he calmed down and went to help Nora. He uses the semblance and then the Grimm doesn't notice them both at all.

Pyrrha (in the Emerald Forest, the same episode as Ren attacking the snake grim) says how everyone's aura is able to protect and help them detect things, so that's not his semblance, that's everyone's auras.

He's probably able to turn off negative emotions, like fear, anger, and sadness, which allows him to be calm in the face of danger, the reason he acts neutral and calm when interacting with everyone else. He also maybe used it to keep him and Nora safe and calm when they were orphaned and alone.

I'm not so sure about this, but maybe he also can get rid of the feeling of tiredness (this is more of a stretch) which is why he got exhausted during the DeathCrawler fight in Players and Pieces. It might be because he was exhausted while fighting (to the point of passing out) so that as soon as he was safe, he was able to do so, or, maybe he just doesn't sleep in general, so he just KO-ed because he never sleeps.