What does Dante find in Circle Five?

Canto VII
Before the poets can leave the travails of the greedy and wasteful behind them, Dante and Virgil must somehow cross the putrid River Styx. They find a passable place and now in Circle Five, where Dante observes a hideous group of sinners. Here they come to the eternal home of the Wrathful. Covered in mud, their sight largely obscured, these souls forever try to wound each other, using their corroded teeth as weapons. Unable to look away, Dante describes the horror:

And I, who stood intent upon beholding,
Saw people mud-besprent in that lagoon,
All of them naked and with angry look.
They smote each other not alone with hands,
But with the head and with the breast and feet,
Tearing each other piecemeal with their teeth.

As if that wasn’t horrendous enough, there is another terrible surprise awaiting Dante. Virgil points out that beneath the first layer of fetid fighting is another crowd of sinners. These souls are those condemned for the crime of being sullen. In life, these people had taken the gift of life for granted, neither appreciating the beauty of being alive nor giving thanks to God. Their punishment is to sing hymns without ceasing, their mouths continually filled with slime that they must swallow. Unable to make out the words, Virgil translates for his companion:

Fixed in the mire they say, 'We sullen were
In the sweet air, which by the sun is gladdened,
Bearing within ourselves the sluggish reek;
Now we are sullen in this sable mire.'
This hymn do they keep gurgling in their throats,
For with unbroken words they cannot say it."

Slowly the pair continue on their journey, coming at last to the foot of a tower.