Here's the Cliff Notes version for our public school viewers
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Summary and Analysis Canto VII
...Dante gets his first glimpse of Circle IV, the circle for the Wasters and the Hoarders. Their punishment is that they are rolling enormous weights at one another, the Wasters shouting, "Why do you hoard?" and the Hoarders shouting, "Why do you waste?" After they clash, the souls hurry their weights back again, only to repeat the action, all the while screaming.
Virgil reminds Dante that time has passed quickly and that they must descend to another circle. They cross to the other bank and find a fountain of strange, dark water, which flows in a stream down through a crack in the rock. Following this stream to the foot of the rocks, they come to the marsh called Styx.
In the Styx, Dante finds people immersed in mud, striking one another with hands, feet, and head, as well as biting one another. Virgil tells him that he is looking at souls destroyed by anger, and that more lie under the waters of Styx, making bubbles with each cry. Virgil repeats their words, which cannot be fully understood. The souls talk of the sullenness of their lives, when they should've been happy in the light of the sun, and that they now live sullen forever. The poets circle the filthy marsh and at last come to a high tower that has no name."
Canto VII