What is nen beast?

Nen beasts are created by skilled Nen users using their aura. They are essentially extensions of the user's own will and can vary greatly in appearance and abilities depending on the user's individual nen ability and personality. Nen beasts can serve a variety of purposes, such as scouting, guarding, attacking, or collecting information. They can also be used to manipulate or deceive others. Nen beasts are most commonly seen in the anime/manga series "Hunter x Hunter."