What are Night Guests?

Occasionally, enemies will randomly appear on your home base. Aside from Invasions, a Night Guest may appear unexpectedly. They have high HP, and will circle around your home if you're inside the house.

It will be difficult to fight this if you don't have the proper items yet, or if your level is low. However, Night Guests will eventually try to destroy your facilities/furniture. Once you see them attack an item, such as your Garden Bed, then you can close in and attack them as well. They won't attack if they're focused on trying to destroy your items.