Some creatures like the Taroc’s ‘walleh’ or the Pterex Bird of the Colibri Islands are thought to be extremely old and powerful demons. Most demons are attached to a particular place rather than a person (though that can happen.) Having lived there for such a long time, they’ve become protective of it. Young demons may be confined to a very small area, even to a single room in a house. As they grow and change, they wander over larger areas and potentially can change shape, though normally they will simply grow additional wings/horns/legs/etc. or change color or markings.