The Ancestor Ghost is an NPC which was added during Harvest Festival 2016. When a player breaks a tree, there is a chance of an Ancestor Ghost spawning. The higher the rarity of the tree, the more likely an Ancestor Ghost will spawn. Ancestor Ghosts will only spawn during Harvest Festival.
If a player leaves a world with an Ancestor Ghost in the world, it will become a regular Ghost when they return. Catching an Ancestor Ghost rewards the player with an Ancestor Mooncake.
The appearance of the Ancestor Ghost is the same as a regular ghost, except that it has a brown colour.