Hunter x Hunter: Chimera Ant Arc

The longest arc in the series, The Chimera Ant arc follows Gon and Killua as they reunite with Kite and are taught about the newly evolved Chimera Ants, a species of rapidly-evolving magical humanoid animals. The boys are tasked with assisting the Hunter Association to eradicate these animals, part of a task-force established by Chairman Netero called the Extermination Team to save humanity.