This begins the path to getting the secret ending of POPGOES: The Dead Forest. Begin by locating a fake wall in the left side of The Castle. Follow the path until it leads you to a chest floating on the water, containing a key. Bring the key out of the North Forest, back to the Fountain located above the Garden Inn and interact with it. This will cause a special sequence to begin. Locate all pieces of the Blackrabbit. There will be one in the Garden, each forest, and The Castle. Bring each piece back to the fountain. Blackrabbit will then tell you to "Come Find Me". This is done by returning to the well in the South Forest and interacting with it. Head left, traversing through all the FNaF 3 Minigames until you find the Blackrabbit boss. Attack it once to get this achievement.