This is something I've often wondered about over the years. The common explanation for Vader's death is, of course, that Sidious' Force Lightening fried the circuits of his suit. But is it really that simple? When Luke says that removing Vader's mask will cause him to die, Vader says: "Nothing can stop that now." Really? In a galaxy full of all kinds of high-tech kit, NOTHING could have saved his life? I've often thought that there is (or was) much more going on. Here's another line from Vader earlier in ROTJ... "You don't know the power of the Dark Side. I MUST obey my Master." This line has always made me think that Vader isn't just serving Sidious at his own free will, but also as a necessity. Vader also sounds a little upset when he says: "It is too late for me, son." I've thought that maybe the original intention was that Vader's life wasn't just attached to the suit, but also to Sidious and his Dark Side powers. Vader, of course, would be aware of this and would know that if Sidious died, he too would die. This would also tie in with the whole thing about Sith being able to keep people from dying. I always thought it would have been good if this was part of the plot of the prequel movies. It also would have made the ROTJ finale all the more emotional - Vader saving his son's life, knowing full well that doing so would cost him his own. Whatever the case, I don't like the whole "Nothing can stop that now" business. That's quitting talk. There's no quit in Vader, damn it! Anyway. I'd love to hear some thoughts.