Retribution is not the main concern of this canto, as it has been in previous cantos, though it is easy to see how at least two of these Giants come to be the guardians of the final circle. Nimrod, the legendary king of Babylon, constructed the Tower of Babel to reach heaven, but he was prevented from doing so by a confusion of tongues. This Giant is damned to spend eternity babbling, without any comprehension of himself or others. The second Giant, Ephialtes, son of Neptune, warred against the gods, and so has his arms bound so that he can do no more harm. The third Giant, Antaeus, is there for the many murders he committed; he should be in another circle, but suffers with the other Giants merely because of his nature as a Giant. Antaeus is the son of Neptune (the sea) and Tellus (the Earth) and was invincible, as long as he touched the Earth, his mother. Hercules killed him by holding him over his head and strangling him in mid-air. He is unchained because he did not join the other Giants against the gods. Here, again, the sinner with the worse sin is punished more harshly.
This canto functions largely as a device to get the poets to the final circle, Cocytus, where Satan resides, and it also serves to introduce the reader to the next division of hell. The Giants serve as another terror that Dante must encounter and can also be read as symbols for the worst that human nature has to offer — these beasts are powerful slaves to their passions. Dante even says that Nature was right when she decided to stop producing them.
The Fallen Angels guarding the gates of the City in Canto VIII are analogous to the Giants guarding Cocytus, as both the Fallen Angels and the Giants are guarding boundaries and serve to link the parts of Lower Hell together. They are also analogous because both groups rebelled against their gods, and the basis of all the sins punished in Lower Hell is Envy and Pride. This canto revolves around the pride of the Giants and also explains the extreme evil of these Giants as intellect joined with brute force and evil will.
