Pentapox

Pentapox is the name of a mock illness invented by Katara in the episode Return to Omashu for escape of the Fire Nation guards for the curfew.

Description
Katara told the guards that it was a deadly and highly contagious illness. The disease is characterized because the person presenting purple stains all over his body. The marks were made with an animal called Purple Pentapus; this animal adheres to the skin, leaving the stains.

History
While in the occupied city of Omashu, Aang, Katara, and Sokka were cornered by Fire Nation guards, who noticed his spots from the Pentapus. Katara said that it was the deadly pentapox, and Sokka put up a dying act that scared the guards away.

Many citizens of Omashu escaped the city through an idea of Sokka. Sokka's plan was to make a false pentapox plague: people had to walk as if they were very ill toward the doors of Omashu. This made the Fire Nation soldiers panic, and on the Governor's orders, they drove the "sickened" civilians out of the city. When word of this reached Princess Azula, she berated the Governor for damaging the Fire Nation's control over the city. She was likely one of the few who did not buy into the ruse.