Who else could the Faithful Slave be? If you don't believe this and obey the Slave, you will be destroyed at Armageddon… unless you die before the great tribulation starts and then you get an automatic pass into paradise.
That is old light. The new light is you have the same chance if you die before or are alive at Armageddon. Only if you are really bad will you not be resurrected or killed at Armageddon