It is reasonable to assume that this map is Ra-Den's room:
Looking at that definitely makes me think Titan-related of some sort.
The entry is from the top portion of the map, and looks like it may be a hidden stairway leading down from the Lei Shen's throne room, so there is certainly the possibility that it's an imprisoned Titan watcher, but I have a different theory.
I believe that Ra-Den is the source of the Thunder King's power. For starters, we all know Blizzard loves its puns, and 'Ra-Den' is pretty reminiscent or Raiden, who we all probably best know as a thunder god from the MK universe (or Raijin if you like, but I'm assuming Raiden is actually the better known reference!). So perhaps Ra-Den is some sort of electric/lightning/thunder Titan weapon that the Thunder King has managed to reign in under his control, siphoning off its power for himself... but with the Thunder King dead, now its power is going out of control.
For starters, that room LOOKS like a prison. The way the map is setup has us entering the central arena via some sort of teleporter or jump pad of some kind from the looks of it, and its a massive raised dias surrounded by an abyss or dead drop. It's even larger than the throne room if those stairs are to scale.