Board Thread:Episode Discussion/@comment-4141313-20181229081856/@comment-4141313-20181230031145

Regarding the loss of Mercury's Semblance, we need to keep several things in mind.

1. It's unlikely Mercury knows the full mechanics of Marcus' semblance, only the bare minimum.

2. Mercury's inspiration is his namesake/Hermes, who was capable of flying with the Talaria, Winged Sandals.

One scenario is that Mercury only thinks Marcus stole his Semblance permanently, and that it didn't return after he killed Marcus due to a psychological block from the abuse at Marcus' hands.

Another scenario is that Mercury's semblance use is tied to his legs, and he can't use it with the prosthetics he has. In the God of War game, Kratos stole the Talaria from Hermes by cutting his legs off, stealing the ability to fly in the process. Since we have seen the CRWBY reference video games before thanks to Li "Hanzo" Ren, they could follow a similar route and have Mercury's loss of his legs be tied to Marcus trying to prevent him from using his semblance.