And now...to introduce you to my take on German folklore cryptid that I definitely plan on using in a book at some point...I started with the general lore about a malevolent field spirit that is destroyed when the last ear of grain is cut, and went from there to flesh out a slightly more...potentially likable being for a protagonist of a future project...
The Roggenwolf is a type of German field spirit that is said to live in farm fields and is often considered dangerous. The Roggenwolf is sometimes equated to the werewolf, but there are several distinct differences. Unlike the 'true werewolf' which is capable, in most old German lore, of shifting forms at will with the use of an enchanted belt, piece of clothing, or wolfskin, the Roggenwolf is tied to the crop cycles of the land. For the purposes of my story, the Roggenwolf can only change forms when there is unharvested grain growing or standing on the field it chooses to bind its magic to. If the owner of that field harvests the last standing grain, the Roggenwolf will be forced to change back to its human form until the field is replanted and the growing cycle begins again, or if they choose to bind themselves to a new plot of land in spring. They cannot alter their magic in harvest time, even if there is a more suitable field nearby. While the forced change is due to magic, there is also a very practical reason the magic exists. Standing grain attracts animals for the Roggenwolf to prey on, and without the relatively reliable food source for its wolf form, the Roggenwolf's magic returning it to a human body is protection for both the wolf and whatever town or village it lives near. As a spirit of cultivated land, the Roggenwolf is by necessity bound to human settlement, and thus must safely co-exist with the humans it lives near, or be destroyed. If it cannot safely and reliably find enough food for its wolf form, becoming human is a sort of defense mechanism against attacking the humans it lives in symbiosis with. While in the past, standing grain was left to appease 'feldgeister' like the Roggenwolf, as times have changed, most people want to harvest as much of their crop as possible. Modern Roggenwolf packs or individuals often own their own farms to ensure that their ties to the land are kept, although some seek out farmland with unharvestable low places in the fields, or farms that leave grain standing to lure deer, turkeys, or other wild animals to hunt.