Dante portrays Satan (also called Lucifer or Dis) as having a body and appearance entirely frightening to Dante.
Dante first sees Satan's gigantic body rising in the distance at the bottom of the frozen Ninth Circle of hell. As he comes closer, Dante is paralyzed with horror. Satan is frozen up to the waist in an icy lake. He has three sets of wings, like those of a bat, and his flapping of them causes the freezing winds to rush around this part of hell. He also has three heads: one is red, one yellow, and one black. In each of his giant mouths he eternally chews on one of the worst sinners in human history: each one betrayed an important benefactor.
In his center mouth, he chews up Judas, who betrayed Jesus, and in the other two mouths, he chews up Brutus and Cassius, who both betrayed Julius Caesar. Only Judas's feet and legs can be seen, as he is placed in Satan's mouth headfirst. The other two are placed in the opposite way, with their faces hanging out. All of these sinners are chewed and ground up by Satan's teeth but never die, so they are forever tortured.
Dante and Virgil cannot stay long in this terrifying place, but Dante is there long enough to realize that Satan is fixed upside down in the ice.