The word «deildegast» name comes from the German word «geist» meaning spirit and “deild” is a name for boundary/border stone. And this touch the theme. In some folk legends it goes under the name «gast». So this is a ghost coming back because they in their lives moved boundary stones or boundary markers to make their own property larger.
The ghost makes an attempt to move the stones back, they can roll a stone up a hill only to find it is rolling down again (yes this we know from a Greek myth). They will have peace when someone puts the stone in place for them. Sometimes they are sees as birds. But what is most striking about them is their sounds. They laugh and cry alternately.
Joh. Th. Storaker Sagn and Gaader (Storakers samlinger VIII)
Once a man came to a mill. He wanted to grind something in the mill. The owner said: «You can try, but the mill stops all the time.»
The man said he would try. He went to the mill, «turned the water on», but the water stopped immediately. Astonished, he went out of the mill. He heard a terrible commotion right by. The miller saw a man who lifted a stone. A stone he tried to get out of the water without being able to do so. The man saw that it was the previous owner of the mill, which had owned both the mill and the woods and fields around. He had been dead for several years. The man asked: «Is it really you who are here?». «Yes,» replied the other; «Could you please help me to place this stone in its place?»
The man took the stone and placed it on the site, where the «gast» pointed. Once he had put the stone down, the other disappeared. Now the mill worked fine.