Cagaster

Cagaster is the disease that began turning humans into giant insects at the end of the 21st century. It was rare, affecting about one in every thousand people, but it was incurable and acted fast. The infected lost their humanity and attacked other people. The resulting transformation was an entirely new species, also dubbed Cagaster, and could breed with other Cagaster. The result: humanity was driven from its cities and mostly decimated.

Cagaster Society
Cagasters quickly grew and multiplied beyond the population of the human race. They eventually attacked cities and grew massive dens known as Cages from the ruins of humanity.

Everything beyond the Eastern Alliance Government, past Western Asia, is known as the Extreme East. It is completely occupied by Cagasters.