A grafter in Dante's "Inferno" refers to someone who sells political favors for money, according to Northern Virginia Community College. A barrator is another term for someone who acquires money by abusing political power. Barrators exist in one of the bottom layers of hell.
Grafters are in the fifth pouch of the eighth circle of hell between fortunetellers and hypocrites. Shmoop states this layer is so dark that Dante compares it to black tar seen in Venice. A black demon that torments these barrators is part of the "Malebranche" or "evil claw" demons that poke and prod the grafters as they boil in black tar. The demons appear to dunk their victims like pieces of meat in stew.
One of the sinners gets a chunk of his flesh ripped out by a demon's hook, much like he took chunks of money from people in Dante's world. This same grafter tries to make a deal with the demons by saying the rest of the barrators can do something for the hellions. Just like real-world grafters, the group being boiled tries to make a deal to get out of their collective punishment. The demons cackle and continue to keep the sinners in the boiling pit.