In canto 3 of Dante's Inferno, Dante encounters those people not fully dead, yet are no longer alive, who wait in the antechamber between Heaven and Hell. Here they're subjected to the meaningless punishment of being repeatedly stung by "gadflies and hornets," and the blood and tears which flow from their bodies is sucked up by "disgusting worms" at their feet. Their meaningless punishment reflects their meaningless lives.
These are the self-serving cowards who refused to use their God-given talents, either for good or evil—"those / Who lived without infamy or praise"—and instead chose a safe middle ground and did nothing. Their lives were wasted and made pointless through no one's fault but their own, and here they simply exist, waiting forever.
These people are "Hateful to God and to his enemies." Heaven rejects them, and Hell refuses to accept them. Heaven exists only for those who consciously chose a good and righteous way of life, and Hell is reserved for those who deliberately chose an evil way of life.
These people, who chose neither good or evil, have no fate other than this, and they must wait forever in the antechamber between eternal bliss and eternal punishment.
Their existence is hellish, but they're not awarded the relief of eternal damnation, nor are they provided any means by which they can rise to Heaven to enjoy eternal happiness.
In canto 3, Dante also sees the souls of the damned waiting for Charon, the ferryman of Hades, to ferry them to the other side of the river Styx that divides the world of the living from the underworld of the dead and damned.
Even though this is just the beginning of his journey, Dante is overcome by terror at what he sees and falls unconscious to the ground.