The Emperor isn't dead, he is immortal because he can transfer his life force to new bodies when the current one is to old or damaged. The same thing Darth Zash was trying to accomplish due to not being able maintain her youthful appearrance and life with force trickery. The Emperors Hand (devout followers only loyal to the Emperor) prepare these bodies and keep the Emperor safe until he regains his strength, while the Emperors Wrath maintains order by exterminating the Emperors enemies & traitors to the Emperors Empire. Darth Nihlus from Kotor2 had similiar plans his goal wasn't just the complete extermination of all Jedi & force sensitives it was total extermination for the ultimate goal of supreme power. He fed off pain & fear not just the force. Unlike Darth Nihlus, the Emperor wants to exterminate life to gain more power but even said it himself that he would let the cycle of life rebuild and start over so as to continue the cycle over for infinity. Totally Mad "yes", Dead "no"!