Vexus meets dr. Edward

Or rather dr. E caught Vexus. Those marks he does to my joker's back will be permanent, and they will be ugly.

Note that he doesn't perform his twisted "art" of combinig machinery with human's flesh just because he wants to torture the joker, or use him as a test subject, but also because this is his way of sending a message to Sigma. A message that when Sigma thinks that he killed dr. E, he is seriously wrong.
Lucky for Vexus, dr. E knows what he is doing, unlucky for the joker is the fact that dr. E makes sure Vexus feels everything.
Those machines dr. E plants to the joker's flesh will keep him alive after that insane suffering... atleast for so long that the message reaches Sigma.

Dr. Edward (c)
Vexus(c) me