Dis was the name given to the capital city of Hell. As one might expect, it was regarded as an infernal place—that is to say, hellish and diabolical. And it is from this dreadful, godforsaken place that Lucifer himself, the Desolate One, has ascended to take one last look at the souls of Dr. Faustus and all the other sinners before they descend to Hell. Lucifer is clearly very excited to know that he will soon be taking full possession of Faustus's soul and can't resist having a little peek at what is about to become his property.
Faustus is a subject of Lucifer's monarchy in that he is soon to become a denizen of Hell. Having turned his back on God, Faustus will soon have a new master: Lucifer himself. And Lucifer, being the epitome of all that is evil, derives enormous satisfaction from knowing that Faustus's mortal soul will soon be hurtling down to the fiery pits of Hell, where it will be tormented for all eternity.
Faustus is spending his last night on earth before his damnation. But instead of just letting him be, Lucifer, along with Beelzebub and Mephostophilis, can't resist coming to him in his hour of darkness and luxuriating in his exquisite torment.