The Cocytus, river of wailing, pools its stinking depths around those who deserve unending torture. This foul swamp offers little reprieve to Sisyphus as he again approaches the summit, thinking that this time may be his last. Here also Ixion turns on his wheel, mud and flies coating his flesh for eternity.
“The foul pool of Cocytus’ sluggish stream lies here; here the vulture, there the dole-bringing owl utters its cry, and the sad omen of the gruesome screech-owl sounds. The leaves shudder, black with gloomy foliage where sluggish Sopor clings to the overhanging yew.” Seneca, Hercules Furens 686 ff (trans. Miller)
"Here a whirlpool boils with mud and immense swirlings of water, spouting up all the slimy sand of Cocytus." Virgil, Aenid 6. 297
"From the lowest realms of Erebeus came the unsubstantial shades, the phantoms of those who lie in darkness . . . round them are the black ooze and unsightly reeds of Cocytus, the unlovely mire enchaining them with its sluggish water…” Virgil, Georgics 4. 471 ff