Bhagavad Gita 16.6द्वौ भूतसर्गौ लोकेऽस्मिन् दैव आसुर एव च।दैवो विस्तरशः प्रोक्त आसुरं पार्थ मे श्रृणु ॥

The two divisions of created beings, the one divine and the other satanic, carry on their respective activities in accordance with their natural tendencies or traits.In the Brihadaranyaka Upanishad also you will find Verily there are two classes of the Creators creatures -- gods and demons (I.3.1).Bhutasargau Creations of beings, types or classes of creatues. Creation here means what is created. The men who are created with the two kinds of nature, the divine and the demonical, are here mentioned as the two creations. Every man in this world comes under the one or the other of the two creations, the divine and the demoniacal.Lord Krishna says to Arjuna, I will now describe to thee the characteristics of those men who are endowed with the devilish alities. If you have an understanding of the demoniacal alities, you will avoid them. The demoniacal nature is described in detail to the very end of this discourse.There is some reference in chapter IX, verses 9, 11 and 12, to the demoniacal nature but as the description is incomplete it is completed in this discourse.The divine nature has been declared in detail by the blessed Lord in the previous chapters -- the state of a Sthitaprajna in chapter II, the state of a Bhagavata in chapter XII and the state of a Trigunatita in chapter XIV and in the first three verses of this discourse.