Ghost

The ghost is a nightly harmless hostile creature that spawns every night in the sky of all worlds.

Behaviour
Ghosts will not attack dwarfs, instead they will seek out the nearest stockpile and toss items around to make a mess. They can move through walls and any other foreground blocks. Ghosts dissipate when the day comes, in a process slightly different from other nightly creatures: it does not need to be touched by the sun light directly: it will be consumed every day at the sunrise, even if it's in a deep and dark underground.

Ghosts may become a serious threat if there is one or more fossilized gargoyle in the stockpile. When a ghost tosses a petrified gargoyle in the night, the gargoyle will be resurrected. If a stone gargoyle is in the stockpile, the ghosts will prioritize throwing these out over everything else.

Pets will ignore ghosts.

Dealing with
Due to their ability to fly and pass through walls, dwarfs may have trouble attacking them. While they pose no physical threat, their ability to toss items is both annoying and time-consuming as they are able to toss items quite far and down holes or mines, requiring dwarfs to fetch them and return them to the stockpile. Items out of the stockpile cannot be used, equipped or consumed.

Ghosts are relatively weak and are best dispatched by any dwarf with a long range weapon. The totem scares ghosts, and they will not move within 5 blocks distant of a totem object, but they will enter totem's area of influence. It is best to build the totem object adjacent to your stockpile.