And Jude is saying this is what can happen to the people now if they do not put themselves in remembrance of these things and turn from these false teachings. The cities, which gave themselves over to fornication, unnatural lusts are set forth as an example. It is not just the cities it is the people within the cities. The city itself can do nothing, the people within her though can. And this is what happens by following Satan eternal fire.
False teachers are dreamers.
They are the ones that defile and harm the soul of the believer. These teachers of false doctrines are of a mind of Satan and have a spirit of heaviness upon them. These teachers have turned from the ways of God and have forgotten the power that God holds. They once ordained are now led by the world. Only God ordains true power and grants true salvation.