He is supposed to be resting but that isn't going to stop him - he's a ridiculously bad patient, despite having been one for so much of his life.

'Still alive' of course means he was assumed dead and there's a huff from Vader and he's almost grinding his teeth - even if he can't quite manage it - his jaw muscles are too damaged.

"Because he's obsessed with me, my progeny, and using us for his own purposes. We're more powerful than he is." Vader's aura grows even colder, Darker, spelling how much he wants to kill, is planning to kill. It's probably not difficult to imagine WHO. The amount of hatred for his Master is actually impressive, even for Sith.