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.
As Dante enters hell under the sign that says, "abandon all hope, ye who enter here," in Canto III, he hears loud noises. These are "strange utterances, horrible pronouncements, accents of anger, [and] words of suffering." They are the sounds made by the great horde of people condemned to live in this ante-chamber of hell.
The real hell is on the other side of the river, where the souls of the damned are ferried across by Charon. This ante-hell is the place where the many people who would not take sides in the great battle between good and evil (God and Satan) are forced to live. They are considered cowards because they were afraid to take a stand while alive, and ignored the need to make moral decisions.
They all run in a circle chasing a banner, while their naked bodies are stung by wasps and other insects. Worms writhing on their bodies then suck the blood and tears from their flesh. Not only do they endure physical torment, they are in mental anguish, actually envious of the people streaming by who get to cross the river into hell. This might be the extreme version of the old saying, "grass on the other side aways looks greener."
One of the people in this part of hell is Pope Clementine V, who resigned after five months, only to be replaced by Dante's hated Pope Boniface VIII.
In Canto III of Inferno, Virgil shows Dante the tortures awaiting "neutral" souls who served neither God nor Satan, and are thus claimed by neither Heaven nor Hell. They are accompanied by the angels who, according to Church tradition, did not choose a side when Lucifer rebelled against God.
Whose lives earned neither honor nor bad fame. And they are mingled with angels of that base sort
Who, neither rebellious to God nor faithful to Him,
Chose neither side, but kept themselves apart
Now Heaven expels them, not to mar its splendor,
And Hell rejects them, lest the wicked of heart
Take glory over them.
Hell's punishments are designed to fit the crime. Since these people wavered during their lives—never choosing a side in the great spiritual war—their punishment is that they must perpetually chase a meaningless banner, all the while being stung and bitten by wasps and flies. They were unwilling to suffer for something that mattered while they were a live, so now they must suffer for something pointless. Moreover, their fate is so meaningless that they envy even the souls who suffer in Hell.