A special class of demons is formed by those which were supposed to infest the resting-places of the dead, though they stand in a certain relationship to the demons that plague the living. A remarkable monument found a number of years ago, and which will be fully described in a subsequent chapter, affords us a picture of some of these demons whose sphere of action is more particularly in the subterranean cave that forms the gathering-place of the dead. They are represented as half human, half animal, with large grotesque and terror-inspiring features.[215] Their power, however, is limited. They are subject to the orders of the gods whose dominion is the lower world, more particularly to Nergal and his consort Allatu. In the advanced eschatology of the Babylonians the demons play a minor part. It is with the gods that the dead man must make his peace. Their protection assured, he has little to fear; but the demons of the lower world frequently ascend to the upper regions to afflict the living. Against them precautions must be taken similar to the means employed for ridding one's self of the baneful influence of the disease-and pain-bringing spirits. Reference has already been made to the spirits that belong to the higher phases of Mesopotamian culture,--those that have a share in the production of works of skill and art. We have seen that in accounting for these we are justified in assuming a higher phase of religious belief. The dividing line between god and spirit becomes faint, and the numerous protecting patrons of the handicrafts that flourished in Babylonia and Assyria can hardly be placed in the same category with those we have so far been considering. Still, to the popular mind the achievements of the human mind were regarded as due to the workings of hidden forces. Strange as it may seem, there was an indisposition to ascribe everything to the power of the gods. Ea and Nabu, although the general gods of wisdom, did not concern themselves with details. These were left to the secondary powers,--the spirits. Hence it happens that by the side of the great gods, we have a large number of minor powers who preside over the various branches of human handiwork and control the products of the human mind. Reserving further details regarding the several classes of demons and spirits enumerated, it will suffice to say a few words about one particular group of spirits whose role was peculiarly prominent in both historical, liturgical, and general religious texts. The tendency to systematize the beliefs in spirits manifests itself in Babylonia, equally with the grouping of the gods into certain classes. In consequence of this general tendency, the conception arose of a group of spirits that comprised the associated secondary powers of earth and heaven, somewhat as Anu, Bel, and Ea summed up the quintessence of the higher powers or gods. This group was known as the Anunnaki and Igigi.