These beings are embodiments of the attitudes of a particular civilisation. Whether they are cause or effect is unknown.
They sometimes survive the death of their people. This only happens when the important places of their civilisation are not occupied by a new group.. In this case they do not leave the location of their former civilisation, but can influence passers-by. Thus a traveller may find themselves moved to sadness by the sight of a particular ruin, as if remembering it in its days of glory, and longing to see them again.
In extreme cases the traveller may have dreams in which they find themselves in a past they never knew, and yet feel themselves to have returned home. They may even gain hints as to where particular treasures, particularly technology and important religious artifacts, may be found. For this last reason, some adventurers will tolerate or even encourage the presence of these spirits.
Some say that Age-Spirits are invisible. Others say that they can choose to appear as an idealised representation of their civilisation. Thus the Age-Spirit of America, for example, might appear as the late Mr Lincoln, an eagle, or as Liberty; while that of England might appear as a lion, or King Arthur.