Interesting! His "Mr. Hyde" has to be something we have not seen. I like your theory of how the writers could work a part-time vampire into the show.

But since Amara is the anchor, her death should destroy the other side. Silas and Amara should both then end up in the afterlife together, with no more other side.

Good theory! Maybe like his Halloween costume Dr. Jekyll, he injects himself with something that turns him to "Mr. Hyde", a vampire here. Perhaps at some point, that side will take over and he will not be able to turn back.

Also, since in this episode Amara and Silas wanted to die, Amara could have asked Silas to drink his blood (the cure), with the promise that they would kill themselves afterwards (presuming Silas would come back to life like Katherine). They would both end up in the afterlife together and the other side would be gone.…