Two ways Marlowe uses suspense in Doctor Faustus are to build fear and to build pity, which coincides precisely with Aristotle's definition of tragedy as drama with "incidents arousing pity and fear" (Poetics, Aristotle). One instance of fear-building suspense comes early on when Faustus challenges Mephistophilis by calling on the name of Christ, an act that instigates the appearance of Lucifer himself.
FAUSTUS. Think, Faustus, upon God that made the world.
Ah, Christ, my Saviour,
Seek to save104 distressed Faustus' soul!
Enter LUCIFER, BELZEBUB, and MEPHISTOPHILIS.
Lucifer's presence on stage has so terrified audiences that it is said they felt the place had been visited by Lucifer himself. This suspense was certainly calculated to increase audience fear.
In what some texts designate as Act V, Faustus' encounter with the Old Man and the Scholars, who try to encourage him to repent and express great sympathy and compassion for him, develops a high level of pity for Faustus as Marlowe uses the suspense in these encounters to show Faustus as repentant, frightened, alone, and ignorant--the one thing he is ignorant of--ignorant of knowing how to ask forgiveness and claim repentance, the ultimate ignorance that dooms him.
FAUSTUS. I do repent; and yet I do despair:
Hell strives with grace for conquest in my breast:
What shall I do to shun the snares of death?
See, see, where Christ's blood streams in the firmament!
One drop would save my soul, half a drop: ah, my Christ!—
Ah, rend not my heart for naming of my Christ!
Yet will I call on him: ...
Where is it now? 'tis gone: