Zygarde is a Legendary Pokémon from the Pocket Monsters series, known for its unique role as the guardian of the ecosystem and balance in the Pokémon world. It is part of the Aura Trio, along with Xerneas and Yveltal, and is capable of changing its form depending on the number of Zygarde Cells it has collected. Zygarde plays a crucial role in maintaining order and preventing destruction, often appearing in times of ecological crisis to restore harmony and protect the natural world from threats.